Shellfish Allergy

What is Shellfish Allergy?

An allergy to shellfish (crustaceans and/or mollusks) causes mild to life-threatening physical reactions. It can first occur at any age, but it most often affects adults. Most people with a shellfish allergy are allergic to crustaceans (shrimp, prawns, crayfish, lobster and crab) and not mollusks (oysters, scallops, snails, octopus, squid and clams), and they may only be allergic to one particular kind.

The immune system overreacts to the proteins in shellfish by declaring chemical warfare. These histamines and chemicals can target major structures of the body including the cardiovascular, respiratory and gastrointestinal systems. For some it takes consumption, but for others all that it takes is breathing in shellfish steam.

What are the Symptoms of Shellfish Allergy?

Signs of a shellfish allergy can occur almost immediately to approximately an hour after exposure. Symptoms may include:

  • Itchy skin
  • Hives
  • Inflammation of the lips, throat, tongue and face
  • Tingly mouth
  • Wheezing
  • Stuffy nose
  • Difficulty breathing
  • Dizziness
  • Fainting

It is vital to be aware of the symptoms of anaphylactic shock. Emergency treatment is required. Seek immediate medical help! Symptoms of anaphylaxis may include:

  • Throat narrowing and constricting the airway (serious breathing difficulties)
  • Severe blood pressure drop with shock
  • Unusually fast pulse
  • Lightheadedness, vertigo and/or passing out

Shellfish Allergy Causes

A shellfish allergy is caused by eating one of the three crustacean foods: shrimp, lobster or crab. Most food allergies start in childhood, but this allergy can develop at any age. The condition is more common in and dangerous for adults.

The reaction involves two forms of antibodies. One is an auto antigen, naturally produced by our body, and the second is a foreign antigen introduced to our body from an external source. The external substance containing the foreign antigen is the shellfish protein.

As our immune system interprets the ingested shellfish protein as harmful, our body’s normal defense response is to release antioxidants and histamines – these chemicals cause the allergic reaction.

In some cases, inhaling the allergens or coming in contact with our skin can cause our immune systems to react. When dining out, cross contamination can happen when eateries share cooking utensils to prepare multiple dishes. All it takes is a small measure of shellfish protein to cause an allergy reaction.

How is Shellfish Allergy Treated?

After tests determine an allergy to shellfish, treatment may include:

  • Avoidance of shellfish
  • Antihistamines to combat itching and rash
  • Carrying an epinephrine injector at all times

Cross-contamination may occur when grocery stores, restaurants and other food handlers store or prepare various types of crustaceans and mollusks together. It may be best to avoid all types of shellfish, even when allergic to just one kind. Carefully read labels, and ask questions when in doubt. Also, consider wearing a shellfish allergy medical alert bracelet.

Shellfish Allergy Prevention

The only way to prevent the allergy is to avoid shellfish, including any food products containing even the smallest trace of shellfish. Read the label on packaged foods, since fish stock or seasoning may contain shellfish. Depending on the severity of your allergies, you may need to avoid any place where crustacean shellfish is cooked, boiled or steamed.

There are no medical methods of preventing food allergies. Talk with your doctor about the condition and consider wearing a medical alert bracelet or some form of identification to let others know about your health condition. In cases where parents are not with the child, medical alert IDs offer the caretakers critical information about the condition. Your doctor may prescribe an emergency kit containing an epinephrine pen to stop severe reactions.

Last Reviewed:
October 10, 2016
Last Updated:
November 07, 2017