A. About 25 percent of all people who struggle with allergies develop them after age 30, said Dr. Thomas Puchner, clinical professor of allergy and immunology in the UW-Madison School of Medicine and Public Health.

The adult-onset varieties can be triggered by all of the usual suspects, he said. Outside, it's trees, grass, ragweed, pollen and outdoor mold, while inside it can be dust mites, pets and feathers.

"I see lots of people for the first time in their 30s, 40s and 50s who say, For the last few years, I'm showing a lot of symptoms,'" Puchner said. "In my 10 years as an allergist, my all-time record for a new-onset allergy is 82 years old."

Why this occurs is not completely understood, he said, but it will often closely mirror family history. About 20 percent of all Americans have allergies, but a person's risk is as high as 40 percent if one parent has them, and as high as 60 percent if both parents have them.

"Allergic reactions to antibiotics are actually higher in adults than kids, and that could be a reflection of greater exposure to more and more courses of antibiotics," he said. "The number one and two allergies are penicillin and sulfa."

Certain subgroups of kids -- such as those with cystic fibrosis, who take a lot of antibiotics -- also have higher incidences of antibiotic allergies than the average population, he said.

-- Produced in cooperation with University Communications

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