For the lucky majority of Americans who've never suffered from allergies, spring and summer are usually uncomplicated stretches of natural bliss. Unencumbered by watery eyes and runny noses, they get to frolic amongst blooming vegetation or tussle with the denizens of local dog parks with abandon. But every now and then, one of these smug adults will step outside, take a deep breath, and feel a wholly unexpected nasal irritation or a welling of tears for the first time in his or her life.
As these unlucky few soon learn, adults can develop allergic symptoms at any time, even fairly late in life. No one knows for sure how many of us will fall victim to this unexpected pain in the ass, but the risk theoretically hovers over everyone, no matter how remote it may be. And some reports suggest the number of adults suddenly manifesting environmentally triggered sniffles could be on the rise. The reality that one could live life carefree one day and wake up the next in bleary fatigue is hard to contend with, especially when so few of us understand how or why these sudden latter-day allergic responses could be triggered.
An estimated 30 to 40 percent of Americans will likely suffer from allergies at some point, most of them triggered by airborne irritants like pollen outside or pet dander or dust mites inside and only a comparative few of them triggered by foods. According to Stephen Tilles, president of the American College of Allergy, Asthma, and Immunology, these folks are born with a genetic predisposition for allergies, but then triggered when they're exposed to a specific allergen—although sometimes that trigger is dependent on additional, little-understood epigenetic triggers. These allergens, although factually harmless, lead prone immune systems to overreact, producing a glut of histamines that can cause irritation in localized areas, or in extreme causes lead to full-body reactions and life-threatening airway closures. Even mild allergies can still lead to real misery and temporary impairment.
The vast majority of people develop allergies as children, when first exposed to triggering allergens. Some people's allergic responses might fluctuate through their teenage years as their bodies—namely their hormones—change rapidly. But Tilles says most people will have developed a stable allergic profile in their 20s. If they "haven't developed allergies by the time they're 30," he adds, "it's very unlikely they're going to [do so] later on." In fact some research actually suggests that as people age their allergies tend to decrease or vanish, although that is unfortunately due to the weakening of the immune system over time.
Beyond this point, Tilles says, most people will only develop allergies if they make a major life change, like a move to a new region, that finally exposes them to a substance they've always been predisposed to have an allergic reaction to. It's also possible that people who haven't moved or encountered a new environment are just manifesting allergies they had when younger, but then went dormant for an oddly longer period of time (perhaps beyond the usual teenage years of hormonal flux) and were only reactivated by some mysterious trigger.
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It's also possible, some doctors speculate, for someone with perhaps a minor allergic inclination to undergo some health event that causes an upheaval in their immune system later in life that might suddenly make it newly sensitive to an allergen. This could be anything from pregnancy to an infection to a major and sickening stretch of stress. (These events may help explain why some people's latent and forgotten or previously minor childhood allergies surge back, too.)
"We are still humble about this," Tilles says. "We'll still skin test for allergies in elderly patients who come in with new onset symptoms. But it's relatively rare for them to have proven allergic causes [for suffering] if they've never had any. It certainly can happen, but it's not common."
It's far more common, Tilles says, for adults to develop non-allergic nasal allergy symptoms out of nowhere. Although indistinguishable symptomatically from allergies for patients, this issue, which Tilles says accounts for about a third of any allergist's patients, is triggered not by distinct allergens and the antibodies they conjure up but by general irritation. "There are sub-groups that are, for example, only triggered by barometric pressure changes," he explains, "and others that are only triggered by [broad] irritants or something like that. There are others that look like allergic inflammation, but we just can't determine that there's an allergen [at work]."
We do know, Tilles says, that smokers or workers in industrial jobs involving airborne irritants they aren't protected from are at increased risk of "non-allergic rhinitis," as allergists refer to this broad nasal irritation. It's also possible the same factors that re-trigger or newly awaken adult-onset allergies, or play a role in the emergence or development of childhood onset allergies, could trigger lifelong general sensitivity in people who aren't genetically disposed to outright allergies.
Beyond that, it's honestly a bit of a crapshoot who suffers when and who doesn't. Long story short, adult onset allergies aren't really a discrete thing. They're the murky common symptom of a ton of different possible exposures or exacerbations, many of which even the nation's foremost allergists only have a basic grasp on. For those wishing to avoid the unique pain of developing allergic symptoms late in life, that is not useful information. Unless one wants to build a bubble of environmental consistency and can somehow avoid major immune system shifts, the risk of waking up snuffling, fatigued, and miserable will always lurk in life.
But on the limited bright side, Tilles says, allergic symptoms are rarely dangerous. They do suck—massively. Still, there are a number of solid treatments available, many of them over the counter. Most treatments meant for allergies will be effective for non-allergic rhinitis as well. And most irritants can be avoided with a bit of planning. Managing irritant exposure risks and symptoms is far from ideal. We just have to deal with the realities of chaotic bodies as best we can.
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