Skip to content

This information was reviewed and approved by Bruce J. Lanser, MD, MPH (8/1/2015).

Seafood, a high-protein, low-fat food, offers many choices for grilling, frying, baking and fresh food dining. Unfortunately, for a percentage of people, different types of fish and shellfish, no matter how they are cooked, can trigger dangerous allergic reactions.

Fish and shellfish are among the most common foods that trigger severe allergic reactions in adults and older children.

For someone with extreme sensitivity, anaphylaxis may occur, resulting in a sudden drop in blood pressure and swelling of the bronchial tissues, causing severe breathing difficulty. These reactions can arise in seconds and can be deadly. Severe anaphylactic shock is fatal if not treated immediately.

If someone has a life-threatening reaction to one crustacean, such as shrimp, testing usually will show that other crustaceans, such as crab, lobster, and crayfish, will also cause a reaction. This relationship is known as cross-reactivity. Different types of fish may have less cross-reactivity, meaning that someone could be allergic to one type of fish, but not another. The challenge, however, is that it can often be hard to tell one type of fish from another, fish can be mislabeled, and in handling cross-contamination is a significant concern.

The good news about food allergies is that only 3 to 4 percent of adults have a true food allergy of any kind. If you suspect you're among this group, meet with your personal physician and, if necessary, devise a treatment plan.



General allergic symptoms occurring within a few minutes to a few hours of eating shellfish may include the following:

  • itching, tingling and swelling in the mouth and throat;
  • runny nose;
  • sneezing;
  • nausea;
  • vomiting;
  • diarrhea;
  • swelling;
  • hives; and
  • difficulty breathing.



Raw or cooked, fish and shellfish can still cause allergies. For most sufferers, it does not matter how fish/shellfish is prepared since the allergenic proteins in fish and shellfish that causes allergic reactions are not destroyed by cooking.

Even minimal exposure to seafood can cause symptoms for some people. Handling fish or shellfish or inhaling fish or shellfish vapors while walking through a fish market or in a restaurant can cause a reaction in extremely sensitive individuals. Exposure also can occur by eating another food cooked on the same surface as fish and shellfish.

Patients with fish and shellfish allergies need to take extra caution when these foods are being prepared. Fish and shellfish are the only foods for which cooking is known to significantly release the food protein into the air. This means that someone allergic to fish or shellfish can have an allergic reaction just by being close to the food while it is being prepared.


Precautions to Avoid a Reaction

The following precautions can be taken to avoid triggering a reaction:

  • Avoid contact with the food.

  • Inform those around you about your food allergy and wear a medical alert bracelet. Have an allergy action plan for treatment of reactions.

  • Know the medicines used to treat reactions and carry them at all times.

Food allergies may be misdiagnosed without a careful patient history and an appropriate evaluation. For example, if you had just eaten shrimp before a reaction, the assumption might be made that shrimp is the cause of the reaction. It may be the cause, but other potential causes, such as another food or ingredients in a sauce eaten at the same time, need to be considered. Testing may be necessary to determine the source of the problem.

For more than 100 years, National Jewish Health has been committed to finding new treatments and cures for diseases. Search our clinical trials.