What is Shell Fish allergy?


A food allergy occurs when body immune system show hypersensitivity to specific foods. Example of some common food allergens are egg, milk, shellfish, peanut, soya, meat and meat products. And all food allergy are caused by an immune system overreaction.

When a person suffers from “Shellfish Allergy”, their immune system identifies certain shellfish proteins as harmful allergens triggering the production of antibodies which then fight against these foreign particles. These antibody-antigen reactions result your immune system to release histamine and other chemicals that causes allergy symptoms in the body.

Studies have shown shellfish allergy mostly develop in adulthood than early childhood  and according to world-wide survey almost 2.3% U.S. population are mostly affected with this type of allergy.

Types of shellfish

There are several types of shellfish, each containing different proteins:

Crustaceans include crabs, lobster, crayfish, shrimp and prawn.

Mollusks include squids, snails, octopus, clamp, oyster and scallops.

Some people show allergy to only one of them and hence they try to avoid the specific one whereas some people show allergy to all types and should avoid all types of shell fish.  

Mechanism of Allergic reaction

In shellfish (crustaceans and mollusks) the protein tropomyosin found, is considered to be the major allergen responsible for ingestion related allergic reaction. Tropomyosin protein belongs to the family of actin filament binding proteins with different isoforms that can be expressed in muscle and no-muscles tissues. Tropomyosin in crustaceans was first identifies in shrimp by scientist Hoffman in 1981. Due to this antigen-antibody reaction, antibodies trigger the release of chemicals such as histamine to attack this protein tropomyosin leading to a number of symptoms which can be mild to life threatening conditions.

Symptoms of Shellfish allergy

In some, it may take some time to develop the symptoms after eating shellfish whereas in some it may develop within minutes. Symptoms of allergy may include:

tingling in mouth

abdominal pain, nausea

diarrhoea and vomiting

skin reactions such as itching, hives or eczema

congestion in breathing

swelling of face, lips, tongue, fingers

dizziness or fainting

In the most serious cases, a severe life threatening allergic reaction known as anaphylaxis may occur. An anaphylactic reaction requires immediate medical attention. Symptoms of anaphylaxis include:

swollen throat (lump in the throat)

rapid pulse

extreme dizziness or loss of consciousness

severe drop in blood pressure


The only therapy for fish and shellfish hypersensitivity is strict avoidance of shellfish and its product to avoid allergic reactions because even trace amounts of shellfish can lead to severe reaction in some people. And if you are diagnosed by severe allergic reaction to shellfish (anaphylaxis), your doctor will prescribe you to take injection of epinephrine (adrenaline). But if you feel you have any of the above symptoms of shellfish allergy, the best way to prevent is to say a big “NO” to shellfish and its product.



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