Q: My daughter has severe allergies to peanut and tree nuts. We’d like to know if she’s safe to eat shellfish, which she hasn’t yet tried (she’s 8 years old). The allergist advised she could just try shrimp but my husband and I are scared of a possible reaction. Should she have a blood test before trying or what would you recommend?
Dr. Sharma: In general, food allergy guidelines do not advise routine testing to potential food allergens before they are introduced to children at “high risk” of reacting. (“High risk” is defined as children who have underlying severe allergic condition or a family history of food allergy.)
Yet, there are certain cases where an evaluation might make sense. If a child has an underlying food allergy already, such as your daughter’s peanut allergy, testing to foods that are common co-allergies might be helpful if those foods have not yet been successfully introduced. For example, among children with peanut allergy, the most common co-allergies are tree nuts, egg and milk.
Shellfish Co-Allergy Not As Common
However, only about 9 percent of children with peanut allergy also have an allergy to shellfish. So shellfish is not a common co-allergy in those with peanut or tree nut allergy, which is likely why your allergist advised trying it.
If a screening evaluation is performed for a possible co-allergy, it’s important to rely not only skin tests and blood tests, as they may be falsely positive. If the allergist thinks it’s warranted, a supervised oral food challenge would help to definitively determine whether a true co-allergy exists.
Dr. Sharma is an allergist, clinical researcher and associate professor of pediatrics. He is Chief of the Division of Allergy and Immunology at Children’s National Medical Center in Washington D.C. and Director of the Food Allergy Program. Questions submitted will be considered for answer.
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