How close to steam would an allergic person have to be to react?

Published: September 17, 2012

Q. I’m allergic to both nuts and shellfish. While I understand that the ‘smell’ of either of these won’t cause a reaction, I’ve read that cooking steam can result in symptoms, perhaps even anaphylaxis.

But how close to steam would an allergic person have to be to react? For instance, if I’m in a restaurant serving seafood, do steaming plates of food present a risk?

Dr. Scott Sicherer: The answer would depend upon the amount of protein in the steam, your personal degree of sensitivity, whether you have asthma, and the amount inhaled.

The amount inhaled is related to proximity, room size, ventilation and other factors. This issue has not been extensively studied.

One small study attempted to replicate reported allergic reactions to cooking vapors in food-allergic children with asthma by having the children in a 7- by 13-foot room while food was being cooked on a stovetop for 20 minutes. Reactions were replicated in five of nine children.

In those five children, the triggers were fish (three children), chickpea and buckwheat. The four negative tests were to milk (two), fish and egg. Among the five reactions, all the children had asthma symptoms and two also developed hives (chickpea and buckwheat).

Regarding your shellfish allergy, based on the study mentioned and studies of people with occupational asthma related to working with shellfish, it seems clear that shellfish protein can become airborne in steam and may trigger reactions. Therefore, steam coming from plates of hot shellfish could pose a risk.

Dr. Scott Sicherer is a practicing allergist, clinical researcher and professor of pediatrics. He is Chief of the Division of Allergy and Immunology, Jaffe Food Allergy Institute, at the Icahn School of Medicine at Mount Sinai in New York. He’s also the author of Food Allergies: A Complete Guide for Eating When Your Life Depends On It.

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