Photo: Getty Q: I have shellfish allergy, which I found out in college. I began getting reactions to shrimp, lobster, mussels and clams. These allergies were confirmed with allergy testing. What I’m not clear on: Can you eat calamari with a shellfish allergy? I’m unsure whether this is safe. I used to eat calamari before my reactions over the past few years.
Dr. Sharma: Since shellfish 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 first to understand the categories of shellfish. First, there are crustaceans: these include shrimp, crab, lobster, prawns and crawfish.
Secondly, there are mollusks: these include squid or calamari, snails, as well as 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. This makes it possible for the immune system to “see” these different kinds of shellfish as similar.
Reacting to More Than 1 Kind of Shellfish
Based on a few limited studies, about 40 percent of people with allergy to crustaceans may react to other crustaceans. Meantime, 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 avoiding all shellfish if someone has had a life-threatening reaction to any kind of shellfish.
Allergic to Calamari, or Not
For those who have had non-life-threatening reactions to a specific shellfish, an allergist might perform testing to the other shellfish. These would include skin and blood testing. Based on the results of these tests, the allergist is able to decide whether to pursue an oral food challenge to assess whether other types of shellfish may be tolerated.
In your case, you have reacted to both crustaceans and mollusks. This suggests a high likelihood that you might also react to calamari, which is a mollusk. But be sure to discuss with your allergist whether testing to squid should be undertaken based on your specific allergy history.
Lastly, 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 Hospital in Washington D.C. and Director of the Food Allergy Program. Questions submitted will be considered for answer.
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How Can an Adult Develop a Shrimp Allergy?