Description

Shellfish allergy is an abnormal response of the body's immune system to proteins in certain marine animals. Marine animals in the shellfish category include crustaceans and mollusks. Examples are shrimp, crabs, lobster, squid, oysters, mussels, and snails.

Seafood is a common food allergy. Some people with shellfish allergy react to all shellfish, while others react to certain types. The reactions range from mild symptoms such as hives or a stuffy nose — to severe and even life-threatening.

If you think you have a shellfish allergy, talk with your health care provider. The tests can help to confirm the allergy, so that you can take steps to prevent future reactions.

Symptoms

Allergy to seafood in general, the symptoms begin within minutes to an hour after eating or having contact with shellfish. They may include:

  • The hives
  • The itch, the irritation of the skin
  • The Nasal congestion (stuffy)
  • Swelling of the lips, face, tongue and throat or other parts of the body
  • Wheezing or difficulty breathing
  • Cough and breathlessness or a feeling of tightness in the throat
  • Abdomen (abdominal) pain, diarrhea, nausea, or vomiting
  • Dizziness, lightheadedness or fainting

Anaphylaxis

Allergies can cause a severe, potentially life-threatening allergic reaction known as anaphylaxis. It can happen in a matter of seconds to minutes after exposure to something you're allergic to — and gets worse quickly.

An anaphylactic reaction to shellfish is a medical emergency. Anaphylaxis requires immediate treatment with epinephrine (adrenaline) injection, and a follow-up trip to the emergency room. If anaphylaxis is not treated right away, can be fatal.

Anaphylaxis causes the immune system to release a flood of chemicals that can cause you to go into shock. The signs and symptoms of anaphylaxis include:

  • Inflammation of the throat or tongue, or a tightness in the throat (airway narrowing) that makes it hard to breathe
  • Coughing, choking, or gasping for breath with difficulty breathing
  • Shock, with a severe drop in your blood pressure and rapid or weak pulse
  • Severe rash, hives, itching, or swelling
  • Nausea, vomiting, or diarrhea
  • Dizziness, lightheadedness or fainting

When to see a doctor

Seek emergency treatment if you develop signs or symptoms of anaphylaxis.

Consult a health care provider or a specialist in allergies if you have a food allergy symptoms shortly after eating.

Causes

All food allergies are caused by a reaction of the immune system. Your immune system identifies a harmless substance as harmful. This substance is called an allergen. In the shellfish allergy, your immune system mistakenly identifies a certain protein in seafood as harmful. Your immune system is the way in which your body protects itself, so that it produces immunoglobulin E (IgE) antibodies to protect against this allergen. The next time that you come in contact with the molluscs of the protein, these antibodies are a sign that your immune system to release chemicals such as histamine into the bloodstream. This causes a reaction that leads to the symptoms of an allergic reaction.

Types of seafood

There are several types of seafood, each one containing different proteins:

  • The crustaceans include crabs, lobster, crab, shrimp and prawn
  • Molluscs include squid, octopus, mussels, snails, clams, oysters, abalone and scallops

An allergy to shellfish is the most common type. Some people are allergic to only one type of shellfish, but can eat other. Other people with shellfish allergy should avoid all shellfish.

An allergy to fish, such as salmon, tuna, or catfish — this is different seafood allergy an allergy to shellfish. Some people who are allergic to shellfish may still be able to eat the fish, or you might be allergic to both. Your health care provider can help you determine what is safe to eat.

Risk factors

You are at greater risk of developing shellfish allergy if allergies of any type are common in your family.

Although people of any age can develop an allergy to seafood, it is more common in adults. In fact, shellfish allergy is the most common food allergies in adults. Among adults, shellfish allergy is more common in women. Among children, shellfish allergy is more common in children.

Complications

In severe cases, the shellfish allergy can lead to anaphylaxis, a dangerous allergic reaction that can be life-threatening.

When you have a shellfish allergy, you may be at higher risk of anaphylaxis if you have:

  • Asthma
  • Allergic reactions to very small amounts of seafood (extreme sensitivity)
  • History of food-induced anaphylaxis
  • Strong family history of allergy

Anaphylaxis is treated with an emergency injection of epinephrine (adrenaline). If you are at risk of having an allergic reaction to shellfish, you should always carry injectable epinephrine (Auvi-Q, EpiPen, etc.).

Prevention

If you have a shellfish allergy, the only way to prevent an allergic reaction is to avoid all shellfish and products that contain seafood. Even small amounts of shellfish can cause a severe reaction in some people.

Avoid seafood

  • Be cautious when you go out to eat. When you eat at restaurants, always make sure the bread, the oil or utensils used for the molluscs are not also used to prepare other foods, the creation of cross-contamination. It may be necessary to avoid eating at seafood restaurants, where there is a high risk of cross-contamination.
  • Read the labels.Cross-contamination can occur in the shops where other processed foods, or that appears near seafood and during the manufacturing process. Seafood can be a soup of fish or shellfish flavor. Read food labels carefully. Seafood is generally not an ingredient that is hidden. Companies are required to label any product that contains crustaceans, molluscs or other foods that commonly cause allergic reactions. However, these regulations do not apply to the molluscs.
  • Keep your distance. You may need to completely avoid the places where the seafood is prepared or processed. Some people react after touching shellfish or breathing in steam from cooking of seafood.

Read the labels. Cross-contamination can occur in the shops where other processed foods, or that appears near seafood and during the manufacturing process. Seafood can be a soup of fish or shellfish flavor. Read food labels carefully.

Seafood is generally not an ingredient that is hidden. Companies are required to label any product that contains crustaceans, molluscs or other foods that commonly cause allergic reactions. However, these regulations do not apply to the molluscs.

Be prepared

If you have a shellfish allergy, talk with your health care provider about the completion of emergency epinephrine auto-injector and how to use it.

Consider wearing a medical alert bracelet or necklace that lets others know that you have a food allergy.

Iodine or radiocontrast dye

One thing that you don't need to worry if you will be allergic to iodine or radiocontrast material that is used in some imaging tests. Although seafood contains small amounts of iodine, shellfish allergy is not related to the reactions that some people have to radiocontrast material or iodine.

Diagnosis

To find out if you have a shellfish allergy, your health care provider will ask about your symptoms and do a physical examination to identify or rule out other medical problems.

A history of allergic reactions shortly after exposure to the seafood may be a sign of an allergy to shellfish. But the symptoms can also be caused by something else, such as food poisoning.

Allergy testing is the only way to know for sure what is causing your symptoms, so your doctor may recommend one or both of the following tests:

  • Skin test. Small amounts of the proteins found in shellfish are raised on the skin in the arm or in the upper part of the back. Then, you watch for an allergic reaction. If you're allergic, you'll develop a raised bump (hive) at the test site on your skin. This usually takes about 15 to 20 minutes. The allergy specialists usually are better equipped to perform the tests of allergy on the skin.
  • Blood test. A blood sample is sent to a laboratory to measure the immune system's response to a specific allergen. This test measures the response of the immune system to the seafood proteins by measuring the amount of the allergy-causing antibodies in the bloodstream, known as immunoglobulin E (IgE) antibodies.

Medically supervised food challenges can be performed if the diagnosis is not yet clear, after the allergy testing.

Treatment

The only sure way to prevent an allergic reaction to shellfish is to avoid seafood. But despite your best efforts, you can get in contact with shellfish.

If you have an allergic reaction to shellfish (anaphylaxis), you will likely need an emergency injection of epinephrine (adrenaline). If you are at risk of anaphylaxis to seafood, your health care provider may give you a prescription ahead of time and explain how and when to give the injection. Regularly check the expiry date stated on the packaging to make sure that the current.

To carry injectable epinephrine (Auvi-Q, EpiPen, others) with you at all times. Epinephrine is typically given at the first sign of an allergic reaction. A second dose may be necessary if your symptoms return. After using this medication, seek emergency medical attention even if you start to feel better.

Preparing for your appointment

It is likely to start by seeing your family doctor. Or you can be referred directly to a specialist in allergies.

What you can do

Prepare for your appointment by making a list of:

  • The symptoms, including any that may seem unrelated to an allergy
  • The family history of allergies and asthma, including the specific types of allergies if you know of them
  • The drugs, vitamins, herbs, or other supplements you are taking and the dose
  • Questions to ask your health care provider

Questions related to allergy to shellfish include:

  • Are my symptoms likely to be due to an allergy?
  • What I'm going to need allergy tests?
  • Should I see an allergist?
  • Do I need to carry epinephrine?
  • Are there brochures or other educational materials that I can have? What sites do you recommend?

Do not hesitate to ask other questions as well.

What to expect from your doctor

Your doctor may ask you questions, such as:

  • What are the symptoms? How serious are they?
  • When did you realize that your symptoms?
  • Has reacted to shellfish in the past?
  • What kind of seafood you ate?
  • How soon after eating seafood did your symptoms occur?
  • What other foods you eat during your meal? Don't forget to sauces, drinks and side dishes.
  • What did others who dined with you have similar symptoms?
  • Is there a history of allergy in the family?
  • Do you have other allergies, such as hay fever?
  • Do you have asthma or eczema (atopic dermatitis)?

What you can do in the meantime

Avoid eating or touching any type of seafood while you wait for your appointment.

Symptoms and treatment of Shellfish allergy