Aeroallergens

Field of ragweed (Photo credit: Ken Bosma/CC BY 2.0)

The Boy Who Cried "Achoo!" Living with Severe Allergies

The Waiting Game

The doctor will be with you in just a second.”

Elbert Liang nodded politely at the nurse as she closed the door, then shifted his weight on the thin blue mattress, careful not to rip the transparent plastic sheet. His mother sat beside him in a chair by the blood pressure machine, flipping through the pages of a tabloid magazine too quickly to actually be reading them. They waited in light silence, punctured occasionally by a child’s cry in the waiting room or a flushing toilet, knowing full well it would be quite a bit longer than a second.

Both were all too familiar with the inside of a doctor’s office. Ever since he could remember, Elbert had spent quite a bit of time in them, lying on the same blue mattresses under the fluorescent lights as the doctors drew blood and performed tests and made him do quite a bit of waiting. Sometimes it was for his sleep apnea. Sometimes it was for cold-induced asthma. Sometimes it was for a sinus infection. This time, it was for his allergies. He’d had a particularly bad allergic reaction several weeks ago and nearly lost consciousness. Now, he and his mother were waiting for the results of a blood test that measured the amount of antibodies his body overproduced in response to more than a dozen allergens, from dust mites, to pet dander, to tree pollen and fungi. The test would give him a better idea of what exactly he was allergic to. 

Elbert already had a feeling that the results would be pretty bad. He just didn’t realize how bad until the doctor came back in, grey eyebrows raised at the clipboard holding Elbert’s charted results.

“This is one of the worst allergy test results I’ve ever seen,” he finally declared. “You reacted to almost every single thing that we tested for. Normally, if there were just one or two things, you could potentially take a shot monthly to slowly gain immunity, or avoid the triggers entirely.” He paused. “But this—there’s no avoiding this.”

Snot-Nosed Kid

Looking back, it’s kind of tragically ironic that now Emory University senior Elbert didn’t realize he had allergies as a child. He’d always suffered from itchy skin and a stuffy nose, but it was also the only state of health he’d ever experienced growing up. He didn’t have anything else to compare the symptoms to, so he didn’t know any better.

“I remember one time when I was a kid, I went to the doctor, and I remember thinking that my nose was actually particularly un-stuffy that day. When I got there, he told me that I was severely congested,” Liang laughed. “That was confusing to me, because it was one of my better days.” 

That appointment would become the first in a long queue of medical consultations about not only his congestion, but an equally exhausting list of allergy symptoms: itchy and irritated skin, rashes and hives, watery eyes, drowsiness, difficulty sleeping, difficulty breathing, facial swelling, and fatigue. As a child, he’d already been on the receiving end of a skin prick test, which checked for immediate allergic reactions to as many as 40 different substances at once by penetrating the skin’s surface with a series of allergen-coated lancets. About 10-15 minutes after the skin pricks, the nurse observed his skin for signs of allergic reactions.

Normally, if the skin reacted to an allergen or two, it would develop a small red, itchy bump that may look like a mosquito bite. But in Elbert’s case, his reactions to all the allergens were so severe that it was impossible to tell what he was or wasn’t allergic to. His entire back, instead of presenting a neat biological chart of allergy indicators, became a swollen mountain range of red wheals. It was impossible to tell where one swelling stopped and another began, and the nurses had to apply antihistamines to control the inflammation. He and his mother left the appointment that day not knowing much more than Elbert was really allergic to a lot of things, which they couldn’t help but feel they had already figured out for themselves.

I Can Live With That

So the results of the blood test he finally got done his first year in high school were helpful, if a bit of a downer. Elbert simply says that he’s “allergic to everything” for the sake of simplicity, and while the real list of allergens isn’t quite that extensive, there’s no denying it’s long. In varying degrees of symptom and severity, he’ll react to corn, wheat, soy, peanuts, dust mites, shellfish, pollen, animal dander, and almost every single plant and weed. To some, he’ll react with some minor drowsiness or skin irritation. For others, exposure can be more dangerous. For example, the blood test informed him that he is deathly allergic to a specific species of tree, which interestingly to this day he is unable to name or identify. 

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Elbert Liang's daily allergy medication (Photo credit: Emily Li)

Just because Elbert takes some risks, though, doesn’t mean he’s completely defenseless against his body’s overprotective and backfiring immune system. On a daily basis, he arms himself with an arsenal of medications. Singullair, which is normally used to treat asthma attacks, helps to reduce chronic swelling in the airways. Zyrtec, an antihistamine, reduces the effects of natural chemical histamine in the body, which is responsible for a range of allergy symptoms: sneezing, itching, watery eyes, runny nose. Zyrtec D is the leveled-up version of Zyrtec. In addition to antihistamines, it also includes a decongestant that helps keep sinuses clear. And last but not least, Elbert tops off his daily allergy medication sundae with Flonase—a steroid hormone nasal spray that reduces swelling and mucus in the nasal passageway.

Even though they don’t have any physical side effects to the best of Elbert’s knowledge, they certainly have a side effect on his wallet. Flonase is $22.99 for one-month supply, while Zyrtec is $18.99. Zyrtec D is $24.99 for 24 pills of 12-hour relief, and Singullair is $9.99 a month. Altogether, he spends approximately $80 per month or $960 every year for access to a the daily cocktail of chemicals he depends on. And because Elbert has been relying on allergy medication since he was about eight, that’s over $13,000 spent total. Not to mention, these price tags on living with allergies don’t include the lifestyle measures his parents implemented growing up to help minimize his exposure to environmental allergens, like switching out carpets for hardwood floors or hiring services to clean out the house’s air vents. Nor do they factor in the health costs just to conduct allergy testing in the first place. A skin allergy test can cost $60 to $300, and a blood test can cost $200 to $1,000. The rising costs of just living with allergies are a question that many families are forced to grapple with as the price of EpiPens skyrockets. Elbert was lucky that his family had the resources to afford to make drastic changes in order to keep him healthy. 

But even protected by these preventative measures while growing up and defended by a shield of multiple medications, having severe allergies still prevents Elbert today from engaging in certain activities that others might take for granted as a part of living life. To him, taking a walk barefoot in the grass would be an invitation for his skin to flare up in immediate protest. He has to take a shower every time he vacuums around his apartment, simply because of the brief exposure to dust mites. He pays for petting a cat with skin irritation and itchiness. The long list of prohibited foods like peanuts, breakfast cereal, and tamales that might trigger an allergic reaction have to stay off his menu. He can’t just opt to pass out on a friend’s carpet for a night, unless he wants his alarm clock in the morning to be rapid facial swelling. And don’t even get him started on pollen.

“Pollen is the worst,” he said seriously. “It’s worse than dust. Pollen makes me really drowsy.”

It’s hard to enjoy a nice spring day when you have to take a nap afterwards just for breathing the air.

But it’s not just minor, day-to-day choices Elbert has to think about as a result of his medical conditions. Having severe allergies also affects many of his larger life decisions. For example, before going to college, the average prospective undergraduate might look at a number of factors, including national rankings, campus culture, department offerings and extracurricular opportunities. Elbert had to look into another potential deal breaker: potential allergen exposures. According to him, his allergies were a big consideration for where he was going to college.

“I did a lot of research on the pollen count in Atlanta, and the present trees and weeds,” said Elbert. “It wasn’t the deciding factor, but I did look into it.”

Sick of Allergies

These sacrifices in lifestyle aren’t just in the name of day-to-day comfort and quality of life, important as those elements are: they’re also integral to Elbert’s overall health. He figured this out the hard way, and in some ways, a bit too late. For instance, just like with his allergies, Elbert’s sleep apnea, a serious sleep disorder that occurs when a person’s breathing regularly interrupted during sleep, didn’t get officially diagnosed until he was in eighth grade. Because he was waking up hundreds of times a night, but falling back asleep too quickly to realize, the condition when undetected for most of his childhood, which he mostly remembers as being “extremely tiring.”

There’s two types of sleep apnea, and Elbert was unlucky enough to suffer from both. In those with central sleep apnea, the brain fails to signal the muscles to breathe, due to instability in the respiratory control center. Obstructive sleep apnea (OSA), on the other hand, is caused by some kind of blockage of the airway. For some, the main cause of OSA is excess weight and obesity. During sleep, the soft tissue of the mouth and throat blocks the airway when tongue and throat muscles relax. This same mechanism can happen in the elderly, as these muscles begin to weaken with age. For Elbert, it was due to a combination of enlarged tonsils and inflammation from allergies. Once the condition was diagnosed, the tonsils removed, the medication started and radiation therapy added to reduce inflammation for good measure, his sleep started to improve drastically. But some damage had already been done. To this day, Elbert blames allergy-induced sleep apnea, and lack of oxygen associated with it, for the fact that his little brother is taller than he is.

And the sleeping problems didn’t end there. Part of it is because Elbert still struggles with central sleep apnea, since there’s no real cure for the neurological disorder. The other half of it is because allergies and sleep apnea continue to go hand in hand. Despite adhering to his strict regimen of daily allergy medications, he notices how the occasional blip can lead to a cascading, self-destructive spiral. For example, an illuminating pattern has emerged from his use of nasal spray: towards the ends of the month, when the bottle is less full, sometimes the spray doesn’t come out with the full dose. Coincidentally, this is usually around the same time of month that Elbert starts to get sick.

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Elbert Liang administers nightly dose of Flonase nasal spray medication (Photo credit: Emily Li)

“I think maybe that’s because I’m not able to breathe as well because I’m not getting the full dose,” he said. “Then my sleep isn’t as good, my energy levels are lower, my immune system is decreased and my body is weaker.”

This ripple effect across his physical state, which affects an even wider circle of social, emotional, and mental health, is one of the reasons that Elbert thinks people should take allergies more seriously. 

“One thing that a lot of people don’t realize is that when allergies get super bad, it’s not just like—’oh, my eyes are watering,’ or ‘I have a stuffy nose’—when it’s really bad, it feels like you’re sick. You don’t have any energy and you can’t get up, all you want to do is sleep all day,” Elbert explained. “It’s not as superficial as it might seem.”

Regardless of how inconsequential allergies might seem to an outsider with a less oversensitive immune system, to those who suffer from them, having allergies is more than having to buy a pack of tissues during pollen season. This condition has serious, and sometimes life-altering, economic and medical effects. For the 30 percent of adults and 40 percent of children in the U.S. who have them, allergies aren’t just inconvenient—they’re a way of life. 

Unpacking the Overreaction Why Climate Change is Nothing to Sneeze at

We’ve honestly never yet met somebody who hated winter, but we know that everybody has their own favorite moments of the season. Maybe it’s just witnessing the quiet magic of a white Christmas through frosted windowpanes. Maybe it’s enjoying a warm cup of hot chocolate and a good book, wrapped up in front of a fireplace. Maybe it’s the satisfaction of creating the perfect snowman on the front lawn, indulging in a good old-fashioned snowball fight on the quad with some roommates, or running to take the cross-country skis out of the garage at the first sight of snow.

Or maybe, it’s that you suffer from severe pollen allergies. If so, we’re not surprised that winter is your ultimate MVP. Ragweed persists through the fall, and isn’t checked until winter’s first touch of frost. From then on, the cold of the winter months is able to mostly keep vegetation that is eager to reproduce at bay, until the onset of spring allows for golden grass and tree pollen to take over the skies. And so if you’re a winter-loving allergy-sufferer, you probably also have a bone—or several—to pick with climate change. You’re not the only one that’s noticed what the changing climate is doing to “winter”—in quotations, since winter lovers barely recognize the new season. After all, for the first time in nearly 150 years, Chicago didn’t receive any snow in January or February. And trust us in saying that you’re definitely not alone if you can’t help but notice (read: it’s becoming impossible to ignore) what new changes to the climate—specifically, pollen counts, as well as other allergens—are doing to your body.

The Anatomy of an Allergy

If you have seasonal allergies, you’re closely aware of what that means for you, your body, and your living habits. It means checking the pollen count in the morning when late March starts to roll around. It means always remembering your allergy pills in the morning or paying for it in the afternoon. It might even mean not being able to enjoy a nice spring picnic or running barefoot in the grass. And you jump through all these hoops because you know what happens if you let down your guard and your allergies catch up to you: an exhausting list of symptoms that you know (literally) inside and out. A stuffy and runny nose. Itchy and watery eyes. Sneezing, of course. Sore throat. Cough. Hives and itching. Fatigue. Nausea and vomiting. In some cases, a severe allergic reaction can lead to anaphylactic shock due to throat swelling and difficulties breathing, which can be fatal. But like we said, you might already know this. After all, nobody knows the effects of allergies better than the 30-40 percent (and rising!) of the world’s population that suffer from them.

There’s no debating that allergies are, at best, a nuisance, and at worst, life-threatening. But the question remains: why do they exist at all? Why do so many people’s bodies react so violently to things that seem so harmless? The problem lies in the fact that while your brain might recognize that allergies are usually caused by innocent stimuli, your immune system just doesn’t get it. After all, we all know that there’s nothing inherently dangerous about pollen, animal dander, dust mites, or peanut butter. And most of the time, your body is pretty good at telling the difference between what’s a threat and what’s not. Not only does your immune system draw on a built-in toolbox of nonspecific defense strategies like your skin and your stomach’s highly acidic pH level (innate immunity), but it’s also able to learn and improvise as it develops a “memory” and creates specialized responses to specific threats (adaptive immunity). All together, your immune system’s network of cells, tissues, and organs works together effectively like a well-oiled machine to defend your body around the clock from foreign invaders.

The problem with allergies starts when your adaptive immune system begins to pick up the wrong habits. The blame almost universally falls to the lymphocytes, more commonly known as white blood cells. Even though lymphocytes are usually your body’s most vigilant soldiers, they can also make the occasional (costly) mistake. They are the cells responsible for moving freely through the body and acting as customs agents, checking the passport of every cell they encounter. If they run into a cell that seems suspicious or threatening, like some kind of new bacteria, virus, or fungi, they’ll immediately begin to initiate countermeasures against the antigen, even if that antigen is nothing but an allergen! Because your immune system doesn’t know that, it orders the white blood cells to begin mass-producing antibodiesY-shaped proteins that are specifically engineered to bind to and fight a specific threat. In the case of an allergy sufferer, a specific kind of antibody—immunoglobulin E, or IgE for short—is overproduced. IgE then attach themselves to receptors on the surface of mast cells and basophils throughout the body in a process known as sensitizing exposure.

From then on, every time you are exposed to the allergen, these IgE-coated mast cells and basophils bind to the them and trigger that all-too-familiar, memorized domino effect of allergy symptoms in the body. Both mast cells and basophils are a specific type of white blood cell called a granulocyte, which simply means that they contain small particles or granules within their cell bodies. Every mast cell and basophil is filled with 500 to 1,500 granules that contain more than thirty different allergy-causing chemicals, which are released when multiple allergens begin to bind to the cell surface receptors. One of the released chemicals that you might be most familiar with is histamine, but these Pandora’s Boxes are goody bags filled to the brim with a variety of other biological mediators guaranteed to make your life difficult, like proteases, chemokines, heparins, cytokines, and leukotrienes.

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When your white blood cells are prettier than you are... (Photo credit: NIAID/CC BY 2.0)

To be fair, the intentions are good. The idea is to essentially send out a cry for help and make it easier for reinforcements to get to the war zone. In reality, however, the effects—like vasodilation, or the expansion of the blood vessels, or increased permeability of the capillaries—have far more negative effects than positive. Depending on where the mast cells and basophils are located, the reactions can range from swelling in the skin, to sneezing, itching, and continuous mucus production in the nose, to shortness of breath, wheezing, and coughing in the lungs. Considering that this whole mess was caused by an overprotective immune system sticking to a “better safe than sorry” philosophy, it’s hard not to want to kick yourself when the symptoms kick in.

This explanation is a relatively simplified, crash-course version of the chaos that occurs in your body when it encounters an allergen. We had to skip over some of the more complex ideas (like differentiating different types of lymphocytes, to the specifics of mast cell and basophil degranulation) in the name of refraining from making this website a biology class (but there’s always Khan Academy if that’s the kind of information that you’re looking for. Feel free to explore their sessions and come back when you’re satisfied!). But even so, it’s important to consider not only what scientists do know about allergic reactions, but also what we don’t—and that category is a lot more robust than you might think. We don’t know precisely why lymphocytes get tripped up by certain allergens in the first place, considering that structurally they don’t even resemble bacteria or viruses (although there’s some speculation that some people’s immune systems may mistake the protein sequence in allergens as similar to those of parasites). And we don’t even know why humans evolved to have allergies at all, although there are a couple of hypotheses floating around like pollen: that people happened to be exposed to an allergen while fighting off an actual pathogen, for example, or the hygiene hypothesis, which suggests that kids these days aren’t being exposed to enough bacteria and viruses during early childhood, so their hypersensitized bodies turn to fighting harmless allergens.

But while we’re still figuring out the details of our response to allergens in our evolutionary past, thanks to climate change, we have a pretty good idea of what our future relationship with allergies will look like. Here’s a hint: it might be smart to invest in Kleenex.

Climate Change and Allergies: Harder, Stronger, Faster, not Better

If you suffer from severe seasonal allergies, you may already have firsthand experience of how climate change is making them worse—but even if you’re one of the lucky ones that won the genetic lottery, you could probably make a good guess (if you didn’t pick up on the heavy-handed clues we dropped in the introduction of this section, or the hints from the natural world around you. We don’t know for you, but at least in Atlanta, some trees seemed to have decided against the whole lose-my-leaves-every-winter thing altogether this year).

Think way back to fourth grade science class. All photosynthesizing plants require some fundamental ingredients in order to properly grow, right? Things like sunlight, warmth, carbon dioxide, and water. And climate change, for the most part, has been happy to deliver on some of these key components (the water one is a bit trickier, since climate change is also a big fan of drought. Read our last section on climate change and wildfires for more information!). For example, warmth, as you might know, is a pretty fundamental piece of climate change’s platform, and it’s something pollen-bearing plants are totally on board for since rising temperatures extend their growing season. Already, satellite images of land cover in the Northern Hemisphere have shown an ominous advancement in spring by up to 19 days over the past 30 years. But according to one study from the Harvard School of Public Health, allowing spring to arrive 30 days earlier resulted in a 54.8 percent increase in ragweed pollen production. So whether you’re relying on scientist or groundhog (you already know what we recommend), the fact growing season goes hand in hand with allergy season means you might not necessarily want to be celebrating predictions of an earlier—and longer—spring.

And increasing temperatures don’t just lengthen the growing season across regions. They’re also making it possible for trees and grasses to expand into entirely new territories that used to be too cold for them. And unfortunately, it appears that climate change will favor the expansion of habitat for trees that happen to have more allergenic pollen. Specifically, habitat that highly allergenic oak and hickory tree species can work with may expand northward at the expense of habitat where much less allergenic pine, spruce, and fir trees currently dominate, as the climate becomes too warm for them. These shifts look like they’ll be most dramatic along the Appalachian Mountains, the Northeastern states from Pennsylvania to Maine, in the Upper Midwest, and along the lower Mississippi River. And it should come as no surprise that in a high emissions world, the projected distributions of annual allergenic potential from tree pollen in the United States looks even worse. That said, unfortunately, even in a low emissions scenario, some states won’t be able to avoid the heightened risk for allergen hotspots (we’re so sorry, Iowa).

Besides warmth, climate change is also a happy provider of carbon dioxide. After all, it totally understands the need for it. Not only does climate change love a little (or a lot of) carbon dioxide and other greenhouse gases, but it itself also helps to keep the cycle going. For example, in the Arctic, more than 1 trillion tons of carbon are locked in the region’s frozen soil. As the climate warms and the permafrost begins to thaw, this carbon could be released into the atmosphere in the form of methanewhich perpetuates global warming and in turn thaws more permafrost. Vegetation around the world, however, isn’t complaining about the excess carbon dioxide in the air. As we mentioned earlier, the gas is necessary for all plants that conduct photosynthesis; it’s absorbed, along with water, and transformed into glucose, oxygen, and ultimately chemical energy. So it shouldn’t come as a surprise that plants aren’t complaining. For instance, a study by the U.S. Department of Agriculture grew common ragweed in chambers and controlled the atmospheric carbon dioxide levels that the plants were exposed to. The researchers found that not only does ragweed grow faster as carbon dioxide in the atmosphere increases, but it also produces significantly more pollen. In fact, if fossil fuel emissions continue unabated, they estimated that pollen production is projected to increase by 60 to 100 percent by around 2085 from this carbon dioxide effect alone.

Not to mention, rising carbon dioxide levels not only enhance plant growth and pollen counts, they also seem to be using the extra chemical energy to boost other processes and activities within the plant that weren’t of high priority when carbon dioxide was scarce. For instance, not only will common ragweed grow faster and produce more pollen in a carbon dioxide-saturated atmosphere, but the pollen itself may become even more allergenic than it already is if carbon dioxide continues to increase. One study found that production of Amb a 1, the main allergenic protein in ragweed that triggers an allergic reaction, increased by 70 percent when dioxide levels were increased from the current level of about 385 parts per million to 600 parts per million, the levels that we can expect by mid-century if emissions aren’t reduced. 

And even if you’re not allergic to pollen, you still have cause to worry if you’re part of the 85 percent of Americans that are allergic to poison ivy, or more accurately, the plant oil urushiol found in its leaves, stems, and roots. A study by Duke University found that not only does poison ivy grow faster as carbon dioxide in the atmosphere increased, but the plants also produced a more allergenic form of urushiol. These changes are great for plants, but clearly don’t always align in our best interests.

Plants aren’t the only natural allergens that climate change is working to help intensify. Fungus—which are neither plant nor animal, and so have their own unique kingdom—are responsible for more than 200,000 cases of allergic reaction in the United States every year. These rebels not only refuse traditional taxonomical classification, they also reject most seasonal limitations, mostly because they’re happy to move into your basement when winter sets in. Whether fungal spores are infiltrating your lungs outdoors or inside, they’re benefiting from the side effects of climate change just as much as their plant cousins. One experimental study published in the Canadian Journal of Botany, for instance, found that doubling atmospheric carbon dioxide levels led to a 4-fold increase in airborne fungal spores released from leaf litter. Plus, the simultaneous increases in plant growth associated with higher carbon dioxide levels provide a helping hand: the higher amounts of plant biomass provide more fodder for decomposition and nutrient absorption for fungi. 

And true to their adaptable reputation, fungus will benefit from both extreme drought and flood, both of which are expected to become more common as the climate continues to change. Following Hurricane Katrina, hospitals in New Orleans reported an increase in patients with allergy symptoms and childhood asthma from fungal spores enjoying the dampness. And as heavy rainfall and hurricanes are projected to increase and become more severe, we’ll probably see a lot more fungus singing, and reproducing, in the rain. At the same time, the rise of hot and dry conditions might also exacerbate fungal allergies as people increasingly rely on air conditioning, since improper management of these systems can create perfect mold-growing conditions.

Finally, as some of the unluckiest members of the population know, allergies aren’t just for plant (and psuedo-plant) species: some allergens can chase you. And yes, we’re talking about insect stings. For most people, a bee sting is a terrifying but relatively unremarkable occasionthe area that was stung hurts for a few hours and then gets better. But if you’re allergic to the venom, technically referred to as “apitoxin” or “apis virus,” then a quick kiss from a bee, wasp, or yellow jacket becomes a much more serious affair. One sting could lead to a range of reactions, from hives all over the body, to swelling in the face, throat, or tongue, to nausea or diarrhea, dizziness, and trouble breathing. In America’s northernmost state, people are finding out the hard way if they’re deathly allergic to these insect stings. Over the past 50 years, the Allergy, Asthma, & Immunology Center of Alaska found that the state saw a 46 percent increase in insect stings, with some parts of the state suffering from increases as high as 626 percent. In 2006, Alaska saw two unprecedented cases of fatal allergy reactions to yellow jacket stings in Fairbanks.

The culprit is climate change; higher average winter temperatures are helping more yellow jacket queens to survive. Significant increases in the number of insect stings across Alaska were seen in regions where the average annual temperature increased 3.4 degrees Fahrenheit or the average winter temperature has risen by at least 6 degrees Fahrenheit over the past 50 years. More specifically, what some scientists think is happening is that it’s becoming warm enough to snow. Yes, you read that right: Alaskan winters usually reach the point where it actually becomes too cold to snow, since very cold air can’t hold enough moisture. Warmer winter temperatures allow for more snowfall, which helps insulate insect dwellings. Ultimately, more stinging insects survive the winter and are able to expand their ranges, which increasingly interferes with human habitats. Basically, if you’re an allergen—pollen, mold, poison ivy, or insect venom—climate change could probably do you a couple favors. (And if you really are an allergen, from the allergy sufferers of the world: please reconsider!)

The City in a Forest

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We'd always take 'city in a forest' over 'concrete jungle'--except on high pollen count days (Photo credit: Joisey Showaa/CC BY 2.0)

If you’re living in Atlanta and struggling with allergies, you might feel like you’ve been getting mixed signals. On the one hand, the city in a forest has been breaking records for soaring particles of pollen per cubic meter within the last five years. On the other hand, according to the Asthma and Allergy Foundation of America, Atlanta should start becoming more attractive for allergy sufferers. The foundation releases an annual Spring Allergy Capitals list to publicly shame and raise awareness for cities that struggle with spring allergies. And while Atlanta topped the entire list in 2004, it’s been steadily falling in the ranks ever since—from #61 in 2015, to #70 in 2016. Soon, it seems that we might not even get featured at all. But then again, on the other hand, you’ve been living here for a few years and you swear you’ve been investing more and more on Zyrtec and tissues. If your allergies are supposed to be getting better, your immune system doesn’t seem to have gotten the memo. So what’s up with that?

You’re not the only one that’s confused. Experts that have been recording and researching pollen counts in the metro Atlanta area for decades also aren’t sure why national rankings don’t reflect the numbers they’ve been seeing. Allergist Stanley Fineman MD, who works for the Atlanta Allergy & Asthma Clinictold Atlanta Magazine he was just as taken aback by the drop in rankings as local allergy sufferers. “I don’t know why we’re so far down there on the list,” he told them. “In terms of pollen count per se, we’re probably up there with anybody. If you’re the patient struggling with their allergy symptoms, it doesn’t matter where Atlanta ranks on that list. If it happens to you, it’s major.” But this insistence on Atlanta’s allergenic attributes isn’t just speculation; it’s rooted in fact. The Atlanta Allergy & Asthma Clinic is not only the largest allergy practice in Georgia; they’re also metro Atlanta’s official pollen count keepers. Their Pollen Counting Station is the only one in the local Atlanta area that’s certified for accuracy by the National Allergy Bureau. And despite interannual variability, they’ve been seeing a very clear, upward trend in pollen counts since they first started measuring in 1992: from an average of less than two extremely high pollen count days in March and April in 1992, 1993, and 1994, to consistently reaching around a dozen of them every year starting in 2013.

Part of the reason for the inconsistency in its reporting may be due to the fact that not only is Atlanta’s pollen season getting more intense, it’s also shifting its timeline. Brad Nitz, a meteorologist at WSB-TV in Atlanta, pointed out on Twitter early last month that the metro Atlanta area reached 1,298 particles of pollen per cubic meter on February 20th of this year. The first time the pollen count got above 1,000 last year was March 17; in 2015, it was March 18, and in 2014, it wasn’t until April 3rd. Basically, the pollen is running more than a month ahead of schedule. Because the first day of spring for the Northern Hemisphere always falls on March 20th or 21st, it’s possible that these earlier peaks in pollen levels are bypassing the Asthma and Allergy Foundation of America’s algorithms for calculating annual Spring Allergy Capitals.

But for allergy sufferers in Atlanta, falling in the notorious ranks are nothing to celebrate. It just means bracing yourself for pollen season to begin as early as February, thanks to climate change pushing spring earlier. And as temperatures continue to stay high into the fall, seasonal allergies will likely overextend their stay. (To be fair, not all of this is climate change’s fault. Heightened aeroallergen counts in the fall are at least partly attributed to the increasing prevalence of Chinese elm trees, which are prized by landscapers and gardeners for their shade, low maintenance, and beauty. And on that note, we know we’ve been talking about climate change like it’s become its own entity, and while in many ways it has taken on a life of its own thanks to feedback loops, here’s your friendly reminder of who got those loops going in the first place: us.)

It might make you feel better to know that you’re not the only one suffering from allergies in Atlanta. After all, misery loves company. But you might be surprised to know that the very fact you can relate to so many people in such a large city helps to contribute to the problem itself. The phenomenon makes Atlanta an “urban heat island”: the scientific term behind why so many Atlantans affectionately refer to the city and her heat as “Hotlanta.” As the population of a city rises, along with urban development and industrialization, so do environmental risk factors that exacerbate climate change and its threats. The most noticeable one of these patterns is temperature. The annual mean air temperature of a city with a million or more people can be 1.8 to 5.4 degrees Fahrenheit warmer than its more rural or suburban surroundings; in the evening, this difference can skyrocket to as high as 22 degrees Fahrenheit. The metropolitan Atlanta area has nearly six million people, but we won’t make you do the math. A study sponsored by NASA’s Earth Observing System Program found that metro Atlanta, on average, sees temperatures up to 10 degrees hotter than surrounding areas, much to the joy of pollen-bearing vegetation in the city limits. There are a lot of reasons for this discrepancy, like he insulating effect of skyscrapers, the “waste energy” from millions of businesses and people going about their daily lives, or the heat-absorbing nature of asphalt and cement compared to lighter, more organic materials.

The end result, however, is pretty simple: cities create and absorb more heat than their less-populated counterparts. And it’s not just heat that gets trapped in there. Invisible local “domes” of high carbon dioxide levels can often hover over urban areas. Together, these higher temperatures and carbon dioxide levels create the perfect conditions for pollen-producing plants (save that five times fast) to thrive. We’re already seeing this, both in reality and in research. Lewis Ziska, Ph.D., a weed ecologist at the Agriculture Research Service division of the U.S. Department of Agriculture, has experienced both. He’s been studying weeds under future climate scenarios in Baltimore, which is already seeing higher local emissions and temperatures compared to rural areas of Maryland. He ran experiments on weeds to mimic climate conditions we’ll likely experience by mid-century if heat-trapping emissions continue as usual: a temperature increase of three to four degrees Fahrenheit, and a concentration of heat-trapping gases of 450 parts per million. The results seemed like they were straight from a sci-fi novel: weeds that grew five and six feet tall in the countryside had counterparts in the city up to 20 feet tall. Can you imagine how much pollen these giants can produce?

Even though the fact Atlanta is a city goes against those of us that suffer from allergies however, the very same allergy producers are the ones that help limit the urban heat island effect: plants. WABE 90.1 reported in 2015 that out of the 50 biggest cities in the country, Atlanta ranked a modest 31st in terms of how intense the heat island effect was. This low score was probably thanks to all the trees. As Atlanta continues to develop, how will events play out? Which one has a greater effect on allergy sufferers: the effects of the urban heat island phenomenon, or the vegetation itself? Will trees give way to concrete and asphalt, or will the push for replanting green the city? Not to mention, normally, climate change and trees don’t really get along, since trees remove carbon dioxide from the air. How do we strike a balance between minimizing pollen allergies, and encouraging carbon sinks?

Forget what we said earlier about the end result being simple: rarely anything about climate change is, especially when it’s centered in a city as confusing as Atlanta (have you tried navigating without your GPS?). But when it comes to allergies in the city in a forest, the bottom line is that you can prepare for them to get worse. The only question is, by how much?

Attacking Allergies Our Own Worst Enemy

Myths and Madness

A hundred years ago, the deserts of the American West were imagined to be a dry, clean haven for allergy sufferers. In the years after World War II, thousands of people who suffered from asthma and allergies flocked to Arizona, seeking—and at first, finding—relief from their symptoms.

According to Gregg Mitman, a medical historian, Tucson in particular aggressively described itself as a health utopia in the 1920s. In his book Breathing Space: How Allergies Shape Our Lives and Landscapeshe discusses how Tucson’s Board of Trade marketed the city’s “pure, dry, invigorating air” and “treasures of health [unlike] anywhere in North America.” John A. Black, Arizona’s commissioner of immigration, said Arizona was a land “where health welcomes the afflicted, and where strength awaits the weak and the suffering.” Approximately half of all people who moved to Tucson in the two decades following World War II did so for health reasons, bringing more than $7 million in annual income to the state from the health and tourist trade. 

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Usery Pass Mountain in Mesa, Arizona (Photo credit: Lone Wadi/CC BY-SA 2.0)

And yet, by the 1970s, pollen levels in Tucson had increased by a factor of 10. The culprits? Urbanization and nostalgia. After millions of new residents made their way to the sunny southwest, they found themselves missing the “civilized” look of many eastern cities from where they came. And so, allergy-prone landscaping and gardening preferences quickly began to colonize the so-called health capital of the United States. For instance, Bermuda grass, a highly reactive allergen, was planted in front lawns. Quickly, it took over town lots and mobile homes, made its way to retirement parks on the city’s edge, and wove along watercourses, all while releasing potent grass pollen. But Bermuda grass wasn’t the only major landscaping change; Eastern tastes for large, shady trees led to the creation of a booming nursery business in exotic ornamental trees. Two particularly allergenic species—mulberry and Russian olive trees—led to the demise of the health-seeking allergy sufferer in Arizona. 

When Tuscon’s newly planted tree population reached maturity in the 1970s, Mitman writes that “the ecological haven had become an ecological hell.” In little more than twenty years, the atmospheric pollen emissions of allergenic plant species in Tuscon had increased tenfold, created by a domino affect that started with landscaping tastes. At the same time, the rapid urbanization of the area created a distinct urban heat island effect, which further exacerbated pollen production and trapped unhealthy levels of air pollution. Altogether, as a result, statistics show that the incidence of asthma in the city became twice the national average at the time, while the incidence of hay fever became six to nine times greater. Some, like Phoenix allergist Dr. William Rieck, believe that genetic factors are partly responsible for the rise in allergy conditions. Because people have traditionally moved to the Arizona area in order to alleviate or escape their allergies, they argue a higher percentage of the population is inherently allergy prone. But this migration alone can not fully explain the increase; environmental factors were also at play.

"The ecological haven had become an ecological hell." Gregg Mitman in Breathing Space: How Allergies Shape Our Lives and Landscapes

This situation wasn’t unique to Tuscon, Arizona. The same story was playing out in different cities across the Southwestern United States at this time: Eastern immigrants suffering from allergies come to seek healthy air, end up in a dry southwestern city, are joined by thousands of other health seekers that exacerbate the urban heat island effect, plant a variety of allergenic species in their backyards, and then complain when their allergies begin to immediately worsen. It was happening in Pheonix, Arizona and Albuquerque, New Mexico; in El Paso, Texas and Las Vegas, Nevada. And even if their own actions were at fault, allergic citizens at the time were understandably upset by what they perceived as a rip-off. But they didn’t want a refund or an apology. They wanted a solution.

What followed was a whirlwind of government regulation that remains, to this day, some of the only instances of pollen allergen management in the United States. There were three primary strategies that local government officials adopted to keep seasonal allergies in check for their residents: zoning, nuisance, and police power.

Zoning describes the control by which an authority, in this case the local government, has the power to establish districts that are restricted to specific types of land uses. Zoning laws might specify a variety of conditional uses of the land, or indicate the dimensions of land area or the scale of buildings. It’s an urban planning technique that helps the government guide urban growth and development so that cities don’t haphazardly sprawl without deliberate direction. (For instance, Houston’s famous lack of zoning laws means long commute times and poor public transit options, which leads to serious health consequences. It also results in some interesting eyesores, like an adult bookstore next to a department store next to a skyscraper.) In the 1970s and 1980s, as resident’s allergies began to act up in earnest, southwestern cities began to take advantage of these laws. By 1970, the city of Tempe in metropolitan Phoenix, Arizona created a zoning ordinance that did not allow developers to plant pollen-producing olive of mulberry trees (although individual landowners were permitted to do so). Similarly, in Tuscon, in order to get zoning approval for new developments, builders are required to use no pollen-producing plants

The second strategy governments used was identifying public nuisances. In general, a nuisance simply refers to any person, thing, or circumstance that causes inconvenience or annoyance. Your mother might have told you to “stop being such a nuisance” when you were misbehaving in a grocery store. When something inconveniences or annoys the government, however, it becomes a pubic nuisance: an art, condition, or thing that is illegal because it interferes with the rights of the general public. For instance, the city of Atlanta lists poison ivy and poison sumac as public nuisances, in addition to “obnoxious gases or odors,” being intoxicated in an airport, and graffiti, to list a few.

To many people, airborne allergens certainly fell into this category. In October of 1975, retired postal worker Herman Berlowe led frustrated, sneezing citizens in lobbying the Tuscon City Council to ban the sale of non-native pollen-inducing trees within city limits. In 1994, against the objection of some nursery owners and developers, the cities of Tuscon and Pheonix responded and officially declared allergenic plants to be public nuisances. Specifically, in both cities, the planting or sale of male mulberry or olive trees was deemed a nuisance, although in 1995, the Tuscon ordinance was amended slightly to allow the planting or two varieties of olive tree that produce less pollen. In addition, Tuscon literally cut back on Bermuda grass. Allowing Bermuda grass to excessively pollinate became a nuisance; residents were essentially required to consistently mow their lawns or face a fine of up to $300 as punishment

Other local governments have relied on police power in order to limit the amount of allergens that infiltrates their cities. Although that might sound severe, crimes related to exacerbating allergy conditions are usually considered to be misdemeanors, or lesser crimes that are tried in the lowest local court. Typical misdemeanors include petty theft, public intoxications, and various traffic violations. In Albuquerque, New Mexico, planting or selling certain trees joins that list of small crimes. And although the punishment might be light, in Albuquerque residents might want to double check their local ordinances before they landscape, considering that the city bans the largest number of plants in the U.S., like male cypress, juniper, mulberry, most poplars and cottonwoods, and most male elms. Certain less allergenic trees are allowed to be sold, but each plant must have an individual label warning of the trees’ pollen production. 

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Mulberry tree (Photo credit: momo/CC BY 2.0)

While zoning, nuisances, and police power are the most common ways that cities in the American Southwest have been controlling local allergens, some regions are toying with other methods of management. For instance, in Las Vegas, Nevada, the government restricts certain allergenic trees as part of its air quality regulation. Clearly, the city wants to be known for sin, not sneezing and sniffling. Since 1991, nobody is allowed to plant or sell male mulberry or European olive trees within the city limits. Commercial growers, however, are allowed to apply for an exemption from the Air Pollution Control Board for low-pollen cultivated plant species.

Besides air quality regulation, some private citizens take it upon themselves to establish community pollen regulations. For instance, if you purchased a condominium, townhouse, or other type of property in a planned development like a leased land property or a gated community, you would be obligated to join that community’s homeowner’s association (HOA) and fees to upkeep. In addition, the HOA has rules and regulations pertaining to the use of land and the look of the neighborhood as a whole. As early as 1975 and even earlier, deed restrictions from an HOA existed against the planting of Bermuda grass, catering to wealthy homeowners that wanted a private “pollen-free, dust-free” zone. In the face of a sickening population and deflating reputations, these were the regulatory tools at the American Southwest’s disposal. 

Scientific Sidekicks

Unfortunately, despite these measures, risks from aeroallergens haven’t significantly decreased since these policies were implemented in the 1970s and 1980s. Southwestern states still suffer from some of the highest pollen counts in the nation. Even though Albuquerque added a pollen-control ordinance banning entire categories of trees in 1994, with violators facing a hefty $500 fine, the city’s Air Quality Division hasn’t seen any major improvements. To be fair, these regions are very proactive (out of necessity) in combatting severe seasonal allergies when compared to the rest of the United States; in many regions, allergens are rarely discussed as an air quality issue, much less implemented or regulated through policy. And between urbanization and climate change, it’s been an uphill battle from the beginning.

Still, it’s never a bad idea to identify areas in which policy can be improved, or just introduced at all in places that lack any regulation. The first call to action there, unsurprisingly, would be to implement government policies that regulate highly allergenic plants, like mulberry and olive trees. Ideally, these species would be banned altogether, either by being named as a public nuisance or making it a crime to sell or plant them, to take a couple leaves out of Arizona’s book.

But some people believe one of the main reasons that progress stalled on the southwest front in terms of pollen counts is because of the number of highly allergenic plant species that were getting grandfathered in each year. In other words, even though it’s a misdemeanor to plant or sell a certain plant, there’s much less regulation against a specific plant that’s already planted in someone’s backyard. In fact, whatever form regulation currently takes, no local government has required landowners to actively remove allergenic plants. Usually, if they exist, they just restrict new plantings. In some cases, this isn’t a big issue. For instance, mulberry trees will die after about 30 years. But olive trees can live for as long as 500 years, emitting pollen the whole time for multiple generations of allergy sufferers to enjoy. With such long-lived allergen producers, the amount of pollen in the air will decline very slowly, if at all.

“We have to wait for those trees to grow to their mature age and die,” Albuquerque City Forester Nick Kuhn told the National Public Radio in an interview for a story on Albuquerque’s decades-long struggle with pollen in 2010. 

For a more effective approach, regulating bodies should mandate the active removal of highly allergenic plant species, in addition to controlling new plantings. If possible, local governments should try to compensate landowners to either incentivize or reward this proactive behavior. Obviously, money is always a good motivator in these cases (and in general, actually). Another option is to offer to replace those highly allergenic species with more allergy-friendly plants, where possible, like the tulip poplar, dawn redwood, or hawthorn. Cities’ best bets are plants that are insect- rather than wind-pollinated, since trees that rely on as fickle a force as wind often produce massive amounts of pollen just in case. Also, using plants that have shorter bloom periods and emit “sticky” pollen, which doesn’t travel as easily through the air, would also help. 

In addition, promoting greater gender equality isn’t just a social issue; in plant and tree nurseries, it could seriously help tip the scales for allergy sufferers. Again, the culprit here is landscaping and gardening preferences, with a pinch of human laziness thrown in: people like plants that aren’t messy. In other words, trees that produce fewer nuts and fruits to clean up. In other words, males. Unfortunately, while male trees might appear to be less maintenance because they are supposedly “litter-free,” they’re also the ones that produce the highest abundance of allergenic pollen. This preference means that most cities are dominated by pollen-spreading male trees. To help combat this, local governments should consider actively buying female trees, since not only do they not produce pollen, female plants also trap and remove pollen from the air. If cities are concerned about street little and clean-up, they can plant sterile female trees, which won’t produce any fruit. And making the switch doesn’t have to be an inconvenient process: according to horticulturalist Thomas Ogren, urban landscapers can simply perform “sex changes” by pruning or grafting male trees into female trees. 

The easily-addressed gender imbalance of plants in our cities isn’t the only case where science could help out the nation’s pollen allergy capitals. Something as simple as spacing trees out slightly could have major differences on annual average pollen counts. In close quarters, tightly-packed communities of trees or shrubs become capable of producing massive amounts of pollen that can’t easily be dispersed by air currents. Everybody loses, especially people with allergies. Instead, researchers from the University of Granada suggest keeping a certain minimum distance between trees.

More scientific studies could also help correct misconceptions in pollen management. For instance, one go-to strategy for city officials is to mandate occasional mowing of allergenic plants, under the assumption that keeping them trimmed will reduce its ability to release pollen. But a recent study of Detroit’s more than 6,000 vacant lots proves this theory wrong. Researchers from the University of Michigan found that the city’s spotty mowing routine—about every one to two years—actually encouraged the growth of ragweed, including its nasty pollen-producing habits. That’s because in undisturbed lots, other plants will quickly outcompete ragweed, but in occasionally managed lots, they never got a chance. In other words, in this case, not mowing at all is preferred over mowing irregularly. 

But in order to suggest these kinds of science-backed policy changes, city officials and researchers need relevant data. One city is already making moves to collect information from its residents to better guide and inform air quality policy. In Louisville, Kentucky’s groundbreaking Asthmapolis project uses a comprehensive mobile network of “smart inhalers” that can track exactly when and where asthma attacks are occurring throughout the city. Government officials can use that information, especially if it’s cross-referenced with other data: maps of Louisville’s tree cover, air quality, and localized heat island effects. This way, the city can identify the asthma and allergy hotspots to focus their public health efforts. Although Asthmapolis is the first of its kind worldwide, hopefully it can inspire other cities to think about how they can collaborate with their citizens to bring them allergy relief. 

Allergies Blow

The hard truth is, there’s no getting away from allergy problems anymore. In other words, everybody is stuck with their own city’s unique set of allergy issues. And that means that everybody has to pitch in and work to reduce the number of allergens in the air, although it may seem fruitless at first to think about ways to limit how an individual personally contributes to their city’s allergy problem. If pollen can just drift in on the next wind, you might wonder, what effect am I really having on my city, and the health of my family?

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Pollen explosion at Monmouthshire, April 2011 (Photo credit: Matt Batchelor/CC BY 2.0)

You would have to consider, however, how gravity applies to pollen. In 1972, Gilbert Raynor, a meteorologist from New York, set up an experiment to determine how allergens organized themselves spatially. He put pollen traps at intervals next to a large stand of timothy grass. And while he was still able to trap some timothy pollen at a mile away from the field, he found the greatest concentration of pollen closest to the field. The bottom line is, the closer you are to a source of allergens, the more pollen you’re exposed to. So if your yard is full of pollen-producing trees and shrubs, you and your family will be the ones that suffer most from them. If the schoolyard your children play in is surrounded by allergenic trees, your children will be the most affected.

In other words, addressing pollen sources near your home isn’t just about doing what’s best for the allergy sufferers in your city: it’s also doing what’s best for you and your family. But it doesn’t hurt that you’re helping to keep pollen out of your neighbor’s lungs too, right?

For most people, that effort starts with the backyard and garden. If you are landscaping your garden from scratch, or if there’s some room in your backyard that you’d like to fill, consider making it a priority to buy allergy-free plants. One useful tool for incorporating the most allergy-friendly species near your home is the Ogren Plant Allergy Scale (OPALS), an allergy rating system for plants that measures the potential of a plant to cause an allergic reaction in humans. The comprehensive strategy analyzes well over 3,000 common trees, shrubs, flowers, and grasses, taking into account not only pollen allergies, but also contact allergies and odor allergies. Within the United States, OPALS has been adopted for use by the American Lung Association and the U.S. Department of Agriculture Urban and Community Forest Service. State governments, like the California Public Health Department, have also endorsed this allergy scale in city landscape planning with the intention of reducing asthma. If governments are taking advantage of it, there’s no reason the average allergy sufferer and homeowner can’t as well.

If you’re not starting from scratch, chances are either you or someone in your family is already feeling the effects of an allergy-rich garden. In that case, short of uprooting your entire landscape, prioritize replacing your biggest culpritspollen-producing male plants and flowerswith pollen-absorbing female ones. The female plants are usually identifiable because they produce fruits, nuts, seeds, or seedpods, while the male ones produce pollen. If replacing all your male plants with female ones seems like too much work, you can also hire a landscaping professional to perform a variety of “sex changes” on male plants so you don’t have to replace them. For mulberry trees, one of the worst allergy offenders, it’s easy to top-graft part of a female tree onto a male one in order to change its sex and pollination habits. You could also plant a tall, allergy-free hedge on the windward side of your property could help block not only pollen grains from the neighbors, but also dust, smoke, and other forms of air pollution that are often responsible for exacerbating respiratory conditions. 

Besides these strategies, however, the best bet for anybody that suffers from allergies is to simply try to avoid their triggers. Medical specialists call this behavior “allergen avoidance”; you might refer to it as common sense. Start by checking the daily pollen counts in your area through a reputable source. in Atlanta, the authority on the matter is undoubtedly the folks at Atlanta Allergy & Asthma, who run a certified daily allergy pollen count for the metro Atlanta area. On high count days, try to avoid going outside for extended periods of time, or interacting with allergenic plant species. Rolling around in the grass with your dog, having a picnic, or climbing trees might be a no-go, depending on how severe the allergy symptoms are. If you’re inside, keep windows and screens closed, especially during the day when plants are especially active. If you have gone outside, remember to take a shower and change your clothing when you come inside.

These might not seem like the most sustainable solutions, especially when considering the worrisome global trends for allergy precedence, and the effects of climate change on highly allergenic environmental triggers. Still, until the condition is taken more seriously and the government takes a more active role in managing allergens and other chronic respiratory irritants, allergy sufferers are mostly on their own in navigating an increasingly pollen-congested world. Try pressuring your local representatives into taking the matter more seriously, and following Southwestern cities by adopting a pollen control ordinance. Talk to your local plant nurseries to start buying more female- and allergy-friendly plant species. Discuss options with your doctors. Everybody should be able to live to their greatest potential year-round—not just when the pollen counts are low.

Chapter section photos of pollen grains against red background and grassy lawn used under Creative Commons licensing from Quinn Dombrowski and Shane Adams, respectively.

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Show Key Terms

Key Terms

Allergen: any substance, usually a protein, that causes an allergic reaction; an aeroallergen is airborne in nature
Sleep apnea: a common disorder when a person's breathing is interrupted during sleep; can be obstructive or central (neurological)
Asthma: a common respiratory condition that causes inflammation and narrowing of the lung's airways, leading to difficulty breathing
Antibody: a Y-shaped protein produced by the body as an immune response to a specific antigen (foreign substance)
Histamine: a natural chemical released by granulocyte cells that causes the symptoms of an allergic reaction
Congestion: an excessive or abnormal accumulation of blood or other fluid in a body part or blood vessel
Anaphylactic shock: an extreme, often life-threatening allergic reaction to an antigen to which the entire body has become hypersensitive
Lymphocyte: a small kind of white blood cell that helps determine the body's immune response to a foreign invader
Granulocyte: a category of white blood cells that contains microscopic granules; includes mast cells and bastophils
Allergenic: having the capacity to cause an allergic reaction
Urban heat island: an urban area that becomes significantly warmer than its surrounding suburban or rural regions
Urbanization: the process of an area becoming increasingly urban
Zoning laws: government regulation that dictates and controls the development and use of land, such as industrial, agricultural, commercial, or residential
Public nuisance: an act, condition, or thing that is deemed illegal because it interferes with the rights of the public generally
Misdemeanor: a minor criminal offense more serious than an infraction and less so than a felony

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