What is a shellfish allergy?

A shellfish allergy is a type of food allergy. If you have a shellfish allergy, you experience unpleasant symptoms after eating shellfish.

Shellfish are animals that live in the water and have a shell-like exterior. There are two types of shellfish:

  • Crustaceans: shrimp, crayfish, crab, lobster.
  • Mollusks: clams, scallops, oysters, mussels.

Is a shellfish allergy the same as shellfish intolerance?

An allergist can figure out if you are allergic to shellfish or have an intolerance. The difference matters. While an intolerance causes uncomfortable symptoms, an allergy can potentially be life-threatening.

Who gets shellfish allergies?

Anyone can develop a shellfish allergy — even if you’ve had shellfish before without any problems. Although it can occur at any age, it appears more often in adults than in children. About 60% of people who have a shellfish allergy first get symptoms as an adult. The reason may be that children typically don’t eat shellfish. People often eat shellfish for the first time as adults, which may be why symptoms appear later in life.

Is a shellfish allergy the same as a fish allergy?

No, shellfish allergies and fish allergies are different. You may have a shellfish allergy but be able to eat fish (and vice versa).

How common is a shellfish allergy?

A study found that approximately 2% of the population (around 6 million people) has a seafood allergy (meaning they are allergic to fish, shellfish or both).

Do all shellfish cause the same reaction?

Often, if you have an allergy to one type of shellfish, you will have an allergy to other types. Crustaceans cause more allergic reactions than mollusks.

You might have a reaction after eating lobster, for example, but eat scallops without a problem. If you have symptoms after eating shellfish, talk with your healthcare provider or allergist before eating any type of shellfish.

Shellfish allergies are sometimes confused with iodine allergies. That’s because shellfish often contains iodine. But having a shellfish allergy doesn’t necessarily mean you’re allergic to iodine. If you have a shellfish allergy, you don’t have to worry about reactions with radiocontrast material. (Certain diagnostic imaging scans use radiocontrast material, which contains iodine.)

What shellfish should I avoid if I have an allergy?

If you have a shellfish allergy, don’t eat these ingredients and foods:

  • Abalone.
  • Clams (such as cherrystone, littleneck, pismo, quahog).
  • Cockle.
  • Conch.
  • Crab.
  • Crawfish and crayfish.
  • Lobster.
  • Mollusks.
  • Mussels.
  • Octopus.
  • Oysters.
  • Scallops.
  • Shrimp and prawns.
  • Snails.
  • Squid (calamari).

What causes a shellfish allergy?

A shellfish allergy, or any food allergy, results from an immune system overreaction. Your immune system defends your body from invaders, such as infections. A food allergy occurs when your body identifies a food substance as a foreign invader and attacks it.

When do symptoms appear?

Typically, allergic reactions to food occur soon after eating the food — within a few minutes to a few hours.

What are symptoms of a shellfish allergy?

Shellfish allergy symptoms range from mild to severe. One person may experience itching and hives while another could have a life-threatening reaction, such as breathing problems. Symptoms can affect many different parts of the body: skin, respiration, digestion and heart.

Shellfish allergy symptoms include:

  • Itching.
  • Hives.
  • Eczema.
  • Tingling or swelling of the lips, tongue or throat.
  • Chest tightness, wheezing, coughing, shortness of breath and difficulty breathing.
  • Stomach issues: pain, nausea, indigestion, vomiting or diarrhea.
  • Dizziness, weak pulse or fainting.
  • Pale or blue skin coloring.
  • Anaphylaxis, a severe, potentially fatal allergic reaction, often involving several parts of the body.

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