What is a Seafood Allergy?
What is a Seafood/Shellfish Allergy?

A shellfish allergy causes an allergic reaction when you eat shellfish. Sometimes, a shellfish allergy is only to certain kinds of shellfish, or you may have an allergy to all shellfish. Shellfish include marine animals with shells, such as shrimp, crab, and lobster, as well as octopus and squid.

Shellfish allergy can cause mild symptoms, such as hives or nasal congestion, or more-severe and even life-threatening symptoms. For some people, even a tiny amount of shellfish can cause a serious reaction.If you think you have a shellfish allergy, talk to your doctor. Tests can help confirm a shellfish allergy, so you can take steps to avoid future reactions.

Symptoms

Shellfish allergy symptoms generally develop within minutes of eating shellfish and include:

Hives, itching or eczema
Swelling of the lips, face, tongue and throat, or other parts of the body
Wheezing, nasal congestion or trouble breathing
Abdominal pain, diarrhea, nausea or vomiting
Dizziness, lightheadedness or fainting
Tingling in the mouth


A severe allergic reaction to shellfish called anaphylaxis can be life-threatening if it interferes with your breathing. An anaphylactic reaction is a medical emergency that requires treatment with an epinephrine (adrenaline) injection and a trip to the emergency room. Signs and symptoms of anaphylaxis include:

A swollen throat or a lump in your throat (airway constriction) that makes it difficult for you to breathe
Shock, with a severe drop in your blood pressure
Rapid pulse
Dizziness, lightheadedness or loss of consciousness



Though they share similar symptoms, a shellfish allergy is different from an adverse reaction to toxins or bacteria in your food. Unlike an allergy, food poisoning doesn't directly involve your immune system and occurs only when you eat food that has been contaminated. An allergic reaction to shellfish usually occurs every time you eat the type of shellfish that causes the reaction.

Causes

All food allergies are caused by an immune system problem. Your immune system identifies certain shellfish proteins as harmful, triggering the production of antibodies to the shellfish protein (allergen). The next time you come in contact with proteins in shellfish, these antibodies recognize them and signal your
immune system to release histamine and other chemicals that cause allergy symptoms.

Histamine and other body chemicals cause a range of allergic signs and symptoms. Histamine is partly responsible for most allergic responses, including runny nose, itchy eyes, dry throat, rashes and hives, nausea, diarrhea, difficulty breathing, and in some cases, anaphylactic shock.

There are several types of shellfish, and each kind contains different allergy-causing proteins. Crustaceans include crabs, lobster, crayfish, shrimp and prawn.

Mollusks include:
Bivalves, such as clams, mussels, oysters and scallops
Gastropods, such as limpets, periwinkles, snails (escargot) and abalone
Cephalopods, such as squid, cuttlefish and octopus


Some people are allergic to only one type of shellfish, but can eat others. However, some people with a shellfish allergy must avoid all shellfish.

Western Medicine Treatment

The only sure way to prevent an allergic reaction to shellfish is to avoid shellfish altogether. Most people with a shellfish allergy can eat fish, however.

Despite your best efforts, however, you may still come in contact with shellfish. If you experience a mild allergic reaction to shellfish, medications such as antihistamines may reduce signs and symptoms, such as rash and itchiness. Antihistamines can be taken after exposure to shellfish to control your reaction and help relieve discomfort.

If you have a severe allergic reaction to shellfish (anaphylaxis), you'll likely need an emergency injection of epinephrine (adrenaline). If you're at risk of having a severe reaction, carry injectable epinephrine (such as an EpiPen, EpiPen Jr.) with you at all times.

Administer an emergency injection of epinephrine if you experience any of these symptoms after exposure to shellfish:

Difficulty breathing
Swollen throat
Wheezing or a repetitive dry cough
Chest tightness
Dizziness, lightheadedness or a feeling that you're going to faint

After you use epinephrine, seek emergency medical care.

Adopted from mayoclinic.com