Allergies are mysterious things, especially considering they affect more than 50 million people in the United States. We have a basic understanding of how allergies work — sufferers produce an antibody called Immunoglobulin E when exposed to substances that are otherwise harmless, like cat dander, peanuts, or ragweed. IgE sets off a chain reaction that results in sneezing, sniffling, and red, itchy eyes.
One of the biggest mysteries is why the disease comes and goes, and then comes and goes again. People tend to experience intense allergies between the ages of 5 and 16, then get a couple of decades off before the symptoms return in the 30s, only to diminish around retirement age.
Three types of explanations have been proposed: environmental, infectious and psychological. But as Mitchell Grayson, an associate professor of allergy and immunology at the Medical College of Wisconsin, points out, they're pretty speculative: "They're not quite hypotheses — there's not even enough evidence to call them that."
Most people live relatively stable lives between birth and 18 years of age. Whatever substances they develop allergic reactions to in their early years are likely to remain in their environment as long as they stay in their parents' home. Once they establish independent lives, though, they may get free of what was ailing them for so many years. College dormitories, while cesspools of infection, are relatively hypoallergenic compared to most homes. Tile floors, cheap, plastic-covered mattresses and the absence of dogs and cats may all contribute to the reduction in allergic symptoms.
A more technical explanation for the disappearance of allergies in the late teens involves viruses. When you infect a mouse with certain viruses, its immune system becomes extremely responsive to IgE. Although our immune systems don't work quite like the immune system of a mouse, there are some tantalizing hints that something similar could be at play in the human body.
Although there isn't much empirical data, some doctors think that the prevalence of allergies and viral infections rise and fall in lockstep as people age. Kids get lots of colds and suffer from allergies. Parents get lots of colds and allergic episodes, too, mostly because they're surrounded by disease-ridden children. A third explanation for the age-related changes in allergies is psychological. Grayson and many other immunologists put the most stock in this theory.
"People in their teens and 20s are interested in chasing other people. That's my politically correct way of putting it," says Grayson. "When you're at that invincible age and out having a good time, you're just not bothered by allergies."
People don't like being told that their symptoms are influenced by psychology in any way. But it doesn't mean they're crazy or faking it. Allergies are real, but how a person experiences the symptoms depends on state of mind.
Any one of these ideas — environmental, infectious or psychological — could explain the undulating experience of allergies through life.
If you're in your 30s and have a history of allergies, you're probably hoping for advice. Unfortunately, there's not much to go on. It appears that the best advice to stave off the return of allergies is either difficult or unpalatable. You could live the life of a vagabond, constantly on the run from the substances that trigger your hyperactive immune system. You could forgo children, in hopes of avoiding the midlife surge of infections that kids seem to bring. You could take a younger person's view of life, finding excitement and possibility in every day. It may distract you from your watery eyes.
Or you can do what everyone else does. "We have drugs to treat allergies," says Grayson. "They work pretty well."