Shellfish Allergy: Causes, Symptoms, and Treatment

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Shellfish Allergy

Imagine you are sitting down to a tasty lobster or a delicious dish of mussels, and suddenly you begin to have a tingling sensation in your mouth region.

Or perhaps your skin begins to itch? You may think it is caused by a new food, but it could be the shellfish you are enjoying even if you have been eating that food for many years with no issues. You may have a shellfish allergy.

Shellfish allergies can begin any time, any place, with any type of the two shellfish varieties, crustaceans or mollusks. Crustaceans are the crab, lobster, crayfish, prawn, shrimp sea creatures while the mollusk group includes clams, mussels, oysters, squid, snails, octopus, cuttlefish, and scallops. Unlike most food allergies that begin in childhood, a shellfish allergy usually happens to adults and is everlasting.

It is important to note that an allergy to shellfish is very different than an allergy to fish. People with fish allergies do not have to avoid shellfish and those allergic to shellfish can still eat fish, in most cases.

In fact, some people only have allergies to one type of shellfish; however, doctors advise to avoid all shellfish if affected by one type or variety. Both fish and shellfish allergies affect more than 6.5 million people nationally, according to the Food Allergy Research and Education (FARE) organization.

Shellfish Allergy Causes

People with shellfish allergies may have been able to enjoy their favorite shellfish dish all of their life before experiencing mild to severe reactions. This is due to the immune system’s response to tropomyosin. This protein is found in the muscle of the shellfish and becomes attacked by the body’s histamine and other chemicals produced by our antibodies.

The result is various symptoms felt by the person consuming the seafood. Furthermore, some people react to this chemical release reaction without even touching or eating shellfish. This happens as the shellfish protein becomes air-borne during the cooking process, and in some restaurants, cross-contamination can occur.

What are the Shellfish Allergy Symptoms?

As with many food allergies, the symptoms can range from mild to severe and even fatal in some cases. With shellfish, symptoms are unpredictable as they may occur immediately or long after coming in contact. Also, each subsequent reaction often becomes worse than the last.

Skin Care HealingSymptoms you may experience:

  • Tingling sensation or swelling in the mouth region or in the throat
  • Itching or hives
  • Nausea, vomiting or diarrhea
  • Dizziness
  • Skin changing to pale or blue-tone color
  • Shortness of breath or wheezing
  • Abdominal pain

The most severe reaction is anaphylaxis, which can affect various parts of the body and can be fatal if not treated immediately. Symptoms include rapid pulse, loss of consciousness or dizziness, difficulty in breathing due to a lump in the throat, and the body experiencing shock from a drop in blood pressure.

How to Treat a Shellfish Allergy

Unfortunately, there is no cure for a shellfish allergy, and the best way to curb any reaction is to avoid shellfish and any places shellfish is served. Although finned fish such as tuna may not present any reactions, there is a chance of cross-contamination with shellfish.
Things to keep in mind if you suspect, or have, a shellfish allergy:

  • Check the ingredients on labels. The Food Allergen Labeling and Consumer Protection Act is a federal law requiring all shellfish products to list the specific type of fish used. Review the label each time as food products are constantly changing.
  • Ask questions about the handling of food at restaurants.
  • Wear an allergy alert medical bracelet.

Discuss your reactions or concerns with your doctor. You may need to carry a self-injectable epinephrine pen for emergencies. Fatal reactions from shellfish allergies may be rare but are more common than other food allergies.

Your doctor may want to conduct allergy tests to confirm your suspicions. A skin test involves pricking the forearm with a tiny amount of the allergen to look for a red, itching reaction. There is also a blood test, radioallergosorbent test (RAST), to measure the immune system’s reaction.

How to Spot Shellfish Allergy Triggers

People with a shellfish allergy must be very careful when dining out or exploring an area where shellfish is present. It is important to remember the shellfish protein can cause an allergic reaction through an air-borne manner with the cooking process. You can also have a reaction from simply handling the shellfish or even touching food that has come in contact with shellfish. In some restaurants, the same cooking oil used to fry shellfish products is used for french fries and deep-fried vegetables. Be mindful of the foods served and ask about the preparation and cooking processes.

Food Labels

Some foods have shellfish products as ingredients such as bouillabaisse, fish stock, surimi, and natural and artificial flavorings. The Food and Drug Administration (FDA) requires food labels to list the top eight allergens that are associated with 90% of the food allergens. Shellfish is one as well as soy, wheat, eggs, peanuts, tree nuts, fish and cow’s milk.

These products must be listed in a separate section of the food label to alert consumers with allergies. However, there is no law stating labels must alert if food products are processed in a facility containing any of these eight allergens. Some companies have taken the initiative and separated the processing units to be able to have it shown on their food products.


We have heard reports of iodine being linked to allergic reactions to shellfish due in part to a Florida family being awarded a $4.7 million lawsuit on behalf of a man dying after receiving iodine during an acute coronary treatment. The man had a shellfish allergy.

In a study comparing shellfish allergens and iodine, it was found iodine is not an allergen, as published in the Journal of Emergency Medicine. From this, there is no concern with a reaction between any radiocontrast material, or iodine, and shellfish allergies.

In today’s world, it seems there are more people suffering from food allergies than ever before. Mild symptoms of shellfish allergy such as itching or nausea are easily treated with over-the-counter allergy medications but more severe reactions such as anaphylaxis shock can be fatal.

As symptoms vary from person to person and gradually become worse from reaction to reaction, those with the allergen must be mindful of their environment at all times. Be sure to talk to your doctor with any questions or concerns if you think you may have experienced a reaction to shellfish.