Most “true” food allergies, including those to seafood, are often lifelong conditions. Seafood allergies trigger a reaction in your body that starts when your immune system mistakenly identifies a protein in shellfish or fish as a threat.
Your immune system creates a defense in the form of immunoglobulin E (IgE) antibodies that react every time your body detects the protein.
Crustaceans are one type of shellfish, and include crab, lobster, shrimp, and crayfish. When you have an IgE antibody-triggered allergy to one type of crustacean, you’re likely to be allergic to others and should avoid these as well.
Mollusks, the other type of shellfish, include clams, oysters, mussels, and scallops. People who get a reaction from a crustacean, such as crab, may be able to eat mollusks, such as oysters, without an issue. Similarly, being allergic to shellfish doesn’t automatically mean you will also get a reaction from eating finned fish because these animals aren’t closely related.
It’s important to ask your doctor for a list of foods to avoid that are specific to your allergy. They may be able to conduct an allergy test that provides more details about the foods that may cause a reaction.
Symptoms of a seafood allergy can vary, and while some are mild, others are potentially life-threatening. Signs to watch out for include:
- Itchy or irritated skin
- Hives
- Swelling of the face, tongue, lips, throat, or other areas of the body
- Nasal stuffiness
- Dizziness, fainting, or lightheadedness
- Coughing and choking, or a tight feeling in the throat
- Wheezing or trouble breathing
- Stomach pain, vomiting, diarrhea, or nausea
In the most severe cases, you may experience a medical emergency known as anaphylaxis, which prompts your immune system to release a large amount of chemicals into your body, possibly resulting in shock. Signs of anaphylaxis include:
- Swollen throat or tongue
- Tightness in the throat or difficulty breathing
- Symptoms of shock, including a rapid or weak pulse and a severe drop in blood pressure
- Choking, coughing, or wheezing with trouble breathing
- Dizziness, fainting, or lightheadedness
- Severe skin rash, hives, itching, or swelling
- Diarrhea, nausea, or vomiting
Even though some anecdotal stories suggest a shellfish allergy as the cause of joint pain, studies haven’t shown this to be true.