Inspired by one of our favorite television shows, Allergy Myth Busters looks at a number of popularly held beliefs about allergy. But are these myths just urban legends or are they true?
MYTH: Adults cannot develop allergies.
While allergies are often thought of as a pediatric issue, adults can clearly develop allergies of all sorts (environmental, food, venom, medication) even when they haven't been allergy sufferers as children. In most instances, such adults likely had a genetic tendency towards allergy and may even have had allergic symptoms such as mild eczema or hay fever as children, but often the symptoms were so mild or long ago that they have no memory of being "allergic" as a child.
There are a number of reasons why adult patients might experience the onset of what appear to be new allergies:
1) Increasing pollen levels - For people with only mild seasonal allergies, the appearance of classical symptoms such as seasonal congestion, runny nose, and itchy/watery eyes might only occur during certain very high pollen seasons. Thus, given that pollen levels have generally been on the rise, such a person might have only recently noticed allergy symptoms as an adult.
2) Move to a new climate or introduction of a new pet - For a patient with an underlying allergic tendency, moving to a new geographic location with vastly different pollens (a new ""aerobiology"") can precipitate the onset of allergy symptoms. Typically, this takes several years to be noted, since one has to be first sensitized to the new allergens in a given location, and then in subsequent years the symptoms occur rapidly with the onset of the pollen seasons in that area. Similarly, a person may not have been aware of a pet allergy, but after significant exposure to a dog or a cat after bringing an animal into the house, a cascade of allergy symptoms can begin.
3) Immune system alteration - There is emerging evidence that exposure to allergens (such as foods or environmental triggers) during times when the immune system is undergoing changes can cause the onset of allergy. The best documented of such immune changes are during certain viral infections, or during pregnancy.
4) Air pollution - Air pollution does not directly cause allergies, but evidence suggests that certain pollutants found in smog might increase the potency of airborne allergens. This effect can lower the threshold of an allergy sufferer who otherwise might not notice the symptoms. More globally, climate change may be contributing to increasing pollen levels and longer pollen seasons, though this hasn't been definitively proven.
5) Foods - Overall, food allergy is significantly more common in children, with certain childhood allergens being very well-known such as peanut, milk, and egg. However, shellfish is a good example of a food allergy that it is much more common in adults than kids. The reasons for this difference are not well-understood, but a new allergy to crab or shrimp in an adult is not a surprising finding for an allergist.
So is the myth busted or true?
Mainly the myth is busted, in the sense that individuals frequently develop allergy symptoms as adults. However, in many instances, there was an underlying tendency towards allergy or even mild allergy symptoms that went unrecognized in childhood.
Dr. David Fitzhugh
Allergy Partners of Chapel Hill