Q: I have shellfish allergy, which I found out in college, by having reactions to shrimp, lobster, mussels and clams. These allergies were later confirmed with allergy testing. What I’m not clear on: would it be safe for me to eat calamari? I did used to eat it before my other reactions over the past three years.
Dr. Sharma: Since seafood allergy is the most common food allergy in adults, there are undoubtedly many others who share your question. For those allergic to shellfish, it’s important to understand the categories of shellfish, which include crustaceans (crab, shrimp, lobster, prawns and crawfish) and mollusks (squid or calamari, snails, and bivalves such as mussels, clams, oysters and scallops).
Several types of shellfish may have similarities in their chemical structure due to a shared protein called tropomysin, making it possible for the immune system to “see” these different kinds of shellfish as similar. Based on a few limited studies, about 40 percent of people with allergy to crustaceans may react to other crustaceans, and 50 percent of those allergic to mollusks report reactions to more than one mollusk. A smaller population, between 10 to 15 percent, are allergic to both crustaceans and mollusks.
Given this information, many allergists will recommend avoidance of all shellfish if someone has had a life-threatening reaction to any kind of shellfish. For those who have had non-life-threatening reactions to a specific shellfish, an allergist might perform testing, such as skin and blood testing, to the other shellfish and then determine based on those results whether to pursue an oral food challenge to assess whether other shellfish may be tolerated.
In your case, you have reacted to both crustaceans and mollusks, suggesting a high likelihood that you might also react to calamari, a mollusk. But be sure to discuss with your allergist whether testing to squid is indicated based on your specific history. Even if you are not allergic to some types of shellfish, you will need to be careful to avoid cross-contact with your allergens in restaurants and fish markets.
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. He co-authors “The Food Allergy Experts” column in Allergic Living magazine. Questions submitted will be considered for answer in the magazine.Submit a Question View all posts by this medical expert.