There you are, digging into some shrimp scampi, a longtime favorite dish, when suddenly you erupt in the weirdest itchy rash. The not-so-nice surprise? You might be allergic to a food you’ve eaten all your life without incident—that is, until now. A new study from the Northwestern University Feinberg School of Medicine found that a surprising 11 percent of U.S. adults have a food allergy, with a substantial number acquiring the allergies as adults. What’s more, 7.2 percent of women reported adult-onset allergy, versus only 3 percent of men.

The uptick may be due to the increased use of antibiotics and sterile environments.

Researchers speculate that the uptick may be due to the increased use of antibiotics and prevalence of sterile environments, as well as rates of C-sections (which are more sterile than vaginal births). “The ‘hygiene hypothesis’ states that the increase of autoimmune and allergic diseases correlates to the increased use of antibiotics and sterile conditions because these practices may lessen our ability to develop immunities,” explains Janna Tuck, MD, a spokesperson for the American College of Allergy, Asthma and Immunology. “By the age of 50, most Americans have had extensive exposure to antibiotics, and potentially that has shifted our immune response.”

The Hives and Other Symptoms

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The symptoms—which generally appear immediately or within several hours of consuming the culprit food—include hives, sneezing, coughing, and difficulty breathing, in addition to becoming nauseated and developing cramps and diarrhea. Life-threatening anaphylaxis can occur; symptoms include a severe drop in blood pressure and airways narrowing dangerously. Yet Dr. Tuck points out that these symptoms can also indicate other conditions, so, “If you suspect that you’ve developed a food allergy, get evaluated,” she says.

For some people, allergies get worse over time.

Should tests conclude a food allergy, there’s no way to tell how serious your next attack could be. “Some people progress over time and others don’t, so a subsequent response could be mild or severe,” says Dr. Tuck. She advises anyone with a food allergy to carry an epinephrine pen to counteract anaphylactic shock, pointing out that “Certain foods, such as shellfish, are easier to avoid than others, like eggs and milk—and accidental exposure does happen.”

Which doesn’t mean we should become food phobic. “While the 11 percent finding is higher than expected, Americans should simply be aware that adult-onset allergies do occur,” says Dr. Tuck. And the great thing about getting tested is that if you learn you’re not allergic, you can safely order that scampi again!