New research shows siblings of children with food allergies have sensitivity, but not true allergy

American College of Allergy, Asthma and Immunology (ACAAI)Nov 5 2015

If one child in a family has a food allergy, the reasoning sometimes goes, chances are good that siblings might also have food allergies. Not necessarily, according to new research which shows that 53 percent of siblings of children with food allergies had a food sensitivity, but only 13 percent had actual food allergy.

According to a study presented at the American College of Allergy, Asthma and Immunology (ACAAI) Annual Scientific Meeting, food allergy testing in siblings of kids with food allergies should be limited to decrease the negative consequences of a potential misdiagnosis.

"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 Ruchi Gupta, MD, MPH, lead study author and ACAAI member. "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."

The 1,120 children included in the study all had a sibling who had a documented food allergy. The food allergy status of the 13 percent of study participants who actually had a food allergy was determined by taking a clinical history to find if there had ever been a reaction to a food, as well as specific IgE (blood test) and skin prick testing. An allergic response to a food can include vomiting or stomach cramps, hives, wheezing, shortness of breath, tightness in the throat, dizziness or feeling faint.

"The risk of food allergy in one sibling, based on the presence of food allergy in another, has never been completely clear," said allergist Matthew Greenhawt, MD, MBA, MSc, ACAAI fellow, and study co-author. "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."