Some children seem to outgrow allergies. But adults who have never had problems with pollen suddenly can start suffering the runny nose and itchy eyes of hay fever. To find out why, we turned to James Sublett, president-elect of the American College of Allergy, Asthma and Immunology, and a practicing immunologist in Louisville, Ky. (Coincidentally, Louisville was identified by medical experts as the most challenging city for allergy sufferers for 2014.)
All in the Family
Allergies are largely genetic. If a parent has allergies, chances are good the children will too. But that doesn't necessarily mean there will be symptoms. What is inherited is an immune system that is predisposed to allergic reactions. And sometimes the symptoms don't emerge until later in life, when exposure to allergens, such as pollen, dust mites or mold, build up over time and reach a critical mass.
Dr. Sublett cites a study of college freshmen who tested positive for the presence of immunoglobulin E, a type of antibody generally associated with allergies, but showed no symptoms. The subjects were checked twice more during their lives.
"Within their college career, about 20% of the students developed some allergies," Dr. Sublett says. When the researchers checked the subjects again 20 years later, they found that 40% had allergies. The conclusion: It takes environmental exposure for people to develop full-blown allergies, even if they are genetically predisposed, Dr. Sublett says.
Come and Go
Dr. Sublett says many factors can trigger the onset of allergies in adults, including high levels of pollution exposure, moving to a home that has mold, adopting a pet or working in a setting where lots of allergens are present. Hormonal changes that come with pregnancy and menopause can also bring on allergies, he says. And in the process of aging, the body's immune system might become more sensitized, which can bring on allergies, he says.
"There are even some viruses that can trigger allergies," Dr. Sublett says. He cites the respiratory syncytial virus, which can infect the lungs and breathing passages, and even the common cold as having the potential to tip the allergy scales in people who are already genetically inclined.
Allergies also can go away when triggers are removed. A change of climate, or getting rid of a pet, might relieve symptoms. On the other hand, after spending a little time in a new city, a person might develop allergies to new types of pollen. "We see that sort of up and down throughout life all the time," Dr. Sublett says.
Hurts at Work
Allergies can be a year-round problem brought on by triggers such as dust mites and furry animals, for example, Dr. Sublett says. Still, people complain about allergies the most during the spring and fall pollen seasons. "There was a study that showed around a 20% reduction in productivity at a call center during the allergy season," he says. "There is a huge social impact."