A seafood allergy is an adverse allergic reaction to eating seafood (including fish and shellfish) that can potentially result in death. It is the third most common type of food allergy and affects almost 3 percent of all adults in the United States, according to the American Academy of Allergy, Asthma and Immunology (AAAAI).

Common symptoms of a seafood allergy include hives, itching, upset stomach and nasal congestion. The most severe cases of seafood allergies can result in anaphylactic shock, a potentially life-threatening reaction characterized by difficulty breathing and a sudden drop in blood pressure.

The only way to prevent an allergic reaction to seafood is to completely avoid seafood, products that contain seafood and even areas where seafood is bought, sold or cooked. Allergic individuals must be aware at all times because even seemingly unrelated food products (e.g., marinara sauce, hot dogs) can contain seafood proteins capable of triggering an allergic response. Some people can have allergic reactions just by inhaling the fumes of cooking seafood or through skin contact with the seafood.

Though many people with seafood allergies are allergic to several different types of seafood, others find they are sensitized to only one type of seafood allergen. Only a physician can determine which types of seafood are safe for a person with a seafood allergy. Tests that may be used for this purpose include skin testing, blood testing, an oral food challenge or an elimination diet.

Because the protein in fish responds well to temperature, cooking fish thoroughly can reduce the potency of its allergens. This can allow some individuals with only minor seafood allergies to consume properly cooked fish without a reaction. However, a patient with a seafood allergy should never attempt to eat any kind of seafood without first consulting a physician.

A type of food poisoning that results from eating spoiled fish is commonly mistaken for a seafood allergy. As fish spoil, they build up histamines, which are the substances in the human body that cause allergy symptoms. Eating spoiled fish can release these histamines throughout the body, causing allergy symptoms without any sort of allergic reaction actually taking place.

In addition, toxins that are often present in the water where fish are caught may cause a reaction or a straightforward case of food poisoning.