Shellfish allergy is a common, but potentially serious food allergy. If you’re allergic to shellfish, your immune system overreacts when exposed to proteins in certain types of seafood. Eating these foods can trigger an allergic response ranging from mild to severe.

A shellfish allergy is separate from a fish allergy. If you’re allergic to fish, you might be able to eat shellfish without having a reaction and vice versa. It’s important to avoid all types of shellfish if you’ve had a previous reaction. Shellfish to avoid includes:

  • clams
  • crabs
  • crawfish
  • lobsters
  • mussels
  • octopus
  • oysters
  • scallops
  • shrimp
  • squid

This type of allergy can affect people of all ages, but it’s more common in adults. A shellfish allergy can also develop over time. Some people are able to eat shrimp and other types of shellfish for years without issue, but then experience an allergic reaction after eating shellfish later in life. Unfortunately, once you develop a shellfish allergy, you’ll probably have the allergy for the rest of your life.

Certain factors increase the risk of shellfish allergy. There’s a higher risk if you have a family history of shellfish allergy. This allergy is also more common in adult women. When it occurs in children, it’s more likely to affect boys.

Because a shellfish allergy can be serious and life-threatening, it’s important to recognize the symptoms and seek immediate medical treatment for a reaction. If you’re allergic to shellfish, symptoms often began within minutes or an hour of eating shellfish. Symptoms can be mild, moderate, or severe. For example:

Mild shellfish symptoms include:

  • itchy skin
  • hives
  • tingling lips
  • nausea
  • coughing
  • stuffy nose

Moderate shellfish allergy symptoms include:

  • wheezing
  • chest tightness
  • abdominal pain
  • diarrhea
  • vomiting

A severe allergic response to shellfish is a medical emergency. These types of reactions can cause anaphylaxis shock, which can be a life-threatening condition. Symptoms of anaphylaxis can include:

  • throat swelling, making it difficult or impossible to breathe
  • drop in blood pressure
  • rapid pulse
  • dizziness
  • loss of consciousness

If you suspect a shellfish allergy, make an appointment with your doctor—even when symptoms are mild. Since a shellfish allergy can worsen over time, you shouldn’t self-diagnose. Your regular doctor may refer you to an allergist for testing.

Your doctor may complete a physical examination, and then ask about your symptoms and the circumstances surrounding your allergic reaction. To make an accurate diagnosis, your doctor may suggest two tests; a skin prick test or a blood test. Testing also helps distinguish a food allergy from conditions with similar symptoms, such as seafood poisoning.

1. Skin prick test. This test examines your body’s response to a suspected allergen. Your doctor pricks your skin with a small amount of the shellfish protein, usually on the forearm or the back of your hand. Your doctor watches your skin to see if hives or raised bumps develop at the prick site. If bumps develop, this can indicate a shellfish allergy. Results are typically available within 15 to 30 minutes.

2. Blood test. This test evaluates how your immune system responds to the shellfish protein, and checks the level of certain antibodies in your bloodstream.

After you’re diagnosed with shellfish allergy, the best treatment is avoiding exposure to shellfish. You’ll have to be extra careful when preparing meals at home and when eating out. Get into a regular habit of reading food labels and avoid any foods containing shellfish. Be aware that some foods contain shellfish products, such as fish stock and artificial seafood flavoring. Realize it’s also possible to have an allergic reaction after handling shellfish or inhaling steam from cooking shellfish.

Whether you’re eating a home-cooked meal or a meal prepared at a restaurant, let food preparers know about your allergy. Even if you don’t eat shellfish, you can have an allergic reaction if your meal is prepared in the same kitchen as meals containing shellfish due to cross contamination. Your non-shellfish meal can come in contact if they use the same grill, or with utensils used to prepare shellfish dishes, or the restaurant may use the same oil to prepare seafood and non-seafood dishes.

If you have a mild or moderate allergic reaction to shellfish, taking over-the-counter antihistamines can reduce your symptoms. Ask your doctor about safe, effective antihistamines. In the case of a moderate or severe allergic reaction to shellfish, an injectable epinephrine (EpiPen) can reverse symptoms of a reaction by opening your airways and stabilizing blood pressure.

If any of your children have a shellfish allergy, it’s important to educate them about their allergy and make sure they understand how to protect themselves. Train your children not to accept food from classmates, neighbors, or anyone else. Notify your child’s teacher or school about the allergy. Even if the school has a stock of EpiPens in the nurse’s office, make sure your children carry their medicine with them at all times, and teach them how to administer the drug.

Like other types of food allergies, a shellfish allergy shouldn’t be taken lightly. Even if you’ve only had mild reactions in the past, make sure you avoid contact with shellfish because your allergy could worsen and become life-threatening as you age.

If you haven’t already, talk to your doctor to see if you’re a candidate for an EpiPen. It’s also helpful to wear a medical alert bracelet or necklace. This can alert others to your allergy if you’re unconscious or unable to communicate after exposure to shellfish.