Is It Possible To Be Allergic To Only Some Kinds Of Shellfish?

A seafood dinner can be a delicious and often even fancy meal experience. For some, though, eating the meal could cause discomfort and may even be life-threatening.

A food allergy occurs when the body reacts to eating something. This reaction is due to the body's immune response to something that entered it, and can take minutes to hours to present an effect (per Mayo Clinic). When this happens, the immune system overreacts to specific proteins in the food and releases histamines that cause unpleasant symptoms (via Uptown Allergy and Asthma). Like numerous other foods, seafood can cause these reactions in many people.

Unfortunately, seafood allergies can start at any time, even if you've eaten the same type of fish in the past. Uptown Allergy and Asthma notes that about 60% of people with a shellfish allergy experience their first symptoms as adults.

The common symptoms that can arise from a reaction to shellfish include swelling, trouble breathing, hives, dizziness, odd skin coloring, vomiting, diarrhea, nausea, and cramps. In more severe cases, anaphylaxis may occur, which causes a drop in blood pressure and can become life-threatening (per Cleveland Clinic).

Luckily when it comes to allergies, not all fish are the same.

Three different seafood types

Crustaceans are the group of seafood responsible for generating the most significant number of reactions. Commonly eaten fish in the crustacean group include shrimp, crab, lobster, and crawfish (via Uptown Allergy and Asthma). Mollusks are another group somewhat similar to crustaceans, including scallops, clams, mussels, and oysters. A third group that stands out because of their lack of shells is finned fish such as salmon, tuna, and halibut.

Diagnosis of a seafood allergy is determined through testing with an allergist. According to the American College of Allergy, Asthma & Immunology (ACAAI), you will be asked questions about the food eaten and the symptoms experienced. Then a blood or skin-prick test will be administered. The skin-prick reveals results within 30 minutes through a small reaction on the skin, while a blood test will measure antibodies present to the food in question, with results taking up to two weeks. 

The ACAAI notes that you can be allergic to one group of fish and not the other. This variable is double-edged since it means you may be able to enjoy some seafood despite an allergy to another, but to do so, you will have to determine whether or not you react to each group.

If you are allergic to any type of fish, the ACAAI recommends consulting an allergist to determine whether it is safe to eat other types of fish. You should also be aware of the risk of cross-contamination, since different types of shellfish are often stored together in markets and restaurants.