In other cases, Gupta said, people have an oral allergy syndrome. That occurs when someone with a pollen allergy has a reaction to a food with proteins similar to pollen — usually a raw fruit or vegetable. The symptoms include itchiness in the mouth or throat, or swelling around the lips.
That type of reaction is not life-threatening, and people may be able to avert it by simply cooking the offending produce, Gupta said.
The study, published online Jan. 4 in JAMA Network Open, included more than 40,400 U.S. adults.
Overall, 19 percent reported food allergies. However, only 10.8 percent had ever suffered “convincing” symptoms — such as hives, throat constriction, lip or tongue swelling, vomiting, difficulty breathing or rapid heartbeat.
Certain other symptoms — like cramps or diarrhea — were not considered convincing, because they are more likely to indicate a food intolerance.
Among people with true allergies, shellfish was the most common culprit: An estimated 3 percent of adults were allergic to shellfish. Milk allergy (1.9 percent) and peanut allergy (1.8 percent) were next in line. Many people had more than one food allergy, the findings showed.
And surprisingly, allergies often developed in adulthood, rather than childhood. Almost half of participants with convincing symptoms developed at least one of their allergies as an adult, according to the report.
It has long been known that adults can develop new food allergies. But Gupta was “really surprised” by how often that was reported in the study.
Shreffler agreed, calling the finding “striking.”
It’s not fully clear why food allergies arise in adults, according to Shreffler. But in some cases, he said, it may be a matter of exposure. Many kids turn their noses up at shellfish, for example — so an allergy might not become apparent until later in life.
Gupta’s team also found that only half of study participants with convincing food allergy symptoms had ever received a formal diagnosis.
Some may self-diagnose and skip the doctor visit, both Gupta and Shreffler said. But it’s also possible for doctors to miss the diagnosis.
“I think that finding is a bit of a wake-up call to the medical community,” Shreffler said.
WebMD News from HealthDay
SOURCES: Ruchi Gupta, M.D., M.P.H., professor, pediatrics, Northwestern University Feinberg School of Medicine, and physician, Lurie Children’s Hospital, Chicago; Wayne Shreffler, M.D., Ph.D., director, Food Allergy Center, Massachusetts General Hospital, and medical advisor, research, Food Allergy Research & Education, McLean, Va.; Jan. 4, 2019,JAMA Network Open, online
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