The Impact of Genetics on Food Allergy Risk

Food allergies may not be equally shared among siblings

Do siblings of food-allergic children have a higher allergy risk themselves? Not necessarily.

A new study from Northwestern University (NU) found that siblings of kids with food allergies may not always share the same allergies. In fact, while 53 percent of the siblings in this study had a food sensitivity, only 13 percent had an actual food allergy.

"Too often it's assumed that, if one child in a family has a food allergy, the other kids need to be tested for food allergies," said lead study author Ruchi Gupta, MD, MPH, an associate professor of allergy and immunology at NU, in a press release. "But testing for food allergies if a reaction hasn't taken place can provide false-positives, as we saw in our research. More than half the kids in the study had a sensitivity to a food, but they weren't truly allergic. Kids who have a food sensitivity shouldn't be labeled as having a food allergy."

John Oppenheimer, MD, a fellow of the American Academy of Allergy, Asthma & Immunology, told RxWiki News that "This reinforces a very important issue in food allergy — a positive skin test does not mean one is allergic. Ideally, food testing is performed as a confirmatory (after a history consistent with a food allergy), not as a screening tool. If we had a reliable screening test for food allergy, we would perform food testing at birth."

According to the American College of Allergy, Asthma and Immunology (ACAAI), more than 50 million Americans have an allergy of some kind, with food allergies estimated to affect between 4 and 6 percent of US children and 4 percent of US adults.

Symptoms of a food allergy can range from mild to severe. The most severe of these is anaphylaxis, a life-threatening reaction that can impair breathing and cause a dramatic drop in blood pressure. If not treated promptly, anaphylaxis can be fatal. Other allergic reaction symptoms include vomiting, stomach cramps, hives, wheezing, shortness of breath, throat tightness, dizziness and swelling.

According to the ACAAI, eight types of food account for about 90 percent of all food allergies. These foods are eggs, milk, peanuts, fish, shellfish, wheat, soy and tree nuts.

For this study, Dr. Gupta and team looked at 876 children who had a sibling with a documented food allergy. The food allergy status of these children was determined by a history of adverse reactions to the allergen, blood tests and skin prick testing.

Dr. Gupta and team found that only 13 percent of these children shared an actual food allergy with their siblings. However, 53 percent had a sensitivity to the allergen.

"The risk of food allergy in one sibling, based on the presence of food allergy in another, has never been completely clear," said study co-author Matthew Greenhawt, MD, in a press release. "This perceived risk is a common reason to seek 'screening' before introducing a high-risk allergen to siblings. But screening a child before introducing a high-risk allergen isn't recommended. Food allergy tests perform poorly in terms of being able to predict future risk in someone who has never eaten the food before. Our study showed that testing should be limited in order to help confirm a diagnosis, rather than as a sole predictor to make a diagnosis."

This study was presented Nov. 5 at the 2015 ACAAI Annual Scientific Meeting. Research presented at conferences may not have been peer-reviewed.

Information on funding sources and conflicts of interest was not available at the time of publication.

Review Date: 
November 4, 2015