Allergies: Shellfish

What is a shellfish allergy?

A shellfish allergy is a type of food allergy. 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.

What fish is shellfish?

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).

Do all shellfish cause the same allergic reaction?

Often, if you have an allergy to one type of shellfish, you’ll have an allergy to other types. Crustaceans cause more allergic reactions than mollusks. But, just because you react one way to one type of shellfish doesn’t mean you’ll react the same way to every single type.

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 before eating any other type of shellfish.

Is a shellfish allergy the same as shellfish intolerance?

An allergist can figure out if you’re allergic to shellfish or have an intolerance. The difference matters. While a food intolerance causes uncomfortable symptoms that mainly affect your stomach or digestive system, an allergy can affect your entire body and 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.

How common is a shellfish allergy?

Approximately 2% of the U.S. population (around 6 million people) has a shellfish allergy.

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 your body like your skin, lungs, digestive system and heart.

Shellfish allergy symptoms include:

• Itching.
• Hives.
• Worsening of 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 your body.

When do shellfish allergy symptoms appear?

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

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.

What are the complications of a shellfish allergy?

The most life-threatening complication of a shellfish allergy is anaphylactic shock, a severe type of allergic reaction. Allergic reactions are hard to predict. Even if you experience a mild reaction the first time, the second allergic reaction could be severe. That’s why it’s important to let your healthcare provider know if you have allergic reactions to any type of food. Your safest bet is to catch an allergy before it surprises you with a life-threatening reaction.

How is a shellfish allergy diagnosed?

Shellfish allergies can be challenging to diagnose. Symptoms differ from person to person, and the same person can have different reactions after eating shellfish. You may have a reaction without even eating shellfish — for example, if you’re cooking it or shellfish contaminates your food.

To diagnose a shellfish allergy, your healthcare provider or allergist will ask you about your symptoms. You may need to answer:

• What did you eat? And how much?
• When did symptoms develop?
• What symptoms did you have?
• How long did symptoms last?

Will I need food allergy testing to diagnose a shellfish allergy?

After asking you about your symptom history, your provider may do food allergy testing to confirm a diagnosis:

• Skin prick test: During this in-office test, your provider places a drop of the allergen on your skin and pricks your skin. The drop seeps into your skin. Your provider will confirm a diagnosis if a red, itchy bump appears after 15 to 20 minutes.
• Blood test: A blood test can help detect whether you have food allergy antibodies but doesn’t diagnose a food allergy.

These tests aren’t conclusive. Together with your symptoms and history, your provider will make a diagnosis.

Will I need an oral food challenge?

Oral food challenges can provide a definitive diagnosis. Under strict, careful supervision, you eat a small amount of the allergen. Your provider increases the dose gradually and notes your symptoms. Occasionally, allergists can use this test to see if you’ve outgrown the allergy. However, most people don’t outgrow shellfish allergies.

How do I manage a shellfish allergy?

You can’t become “un-allergic” to shellfish. The best way to keep yourself healthy is to avoid shellfish. Besides avoiding shellfish itself, make sure you avoid foods that contain shellfish.

The Food and Drug Administration (FDA) requires food manufacturers to list common food allergens, such as shellfish, on food labels. The food label lists the allergen either in the ingredients list or after the list. For example, if a product contains abalone, a species of shellfish, the label will state “abalone (shellfish)” in the ingredients or “contains shellfish” after the ingredients list.

What do I do if I have an allergic reaction?

Epinephrine is the main treatment for anaphylaxis. Once your provider has confirmed a shellfish allergy, you’ll get a prescription for self-injectable epinephrine (EpiPen®). Your provider will teach you how to use it.

If you have a severe allergic reaction and inject yourself with epinephrine, the next step is to call 911. Make sure to tell the dispatcher what happened and that you used your epinephrine injection. Emergency medical technicians (EMTs) may need to give you another dose when they arrive.

When should I use an epinephrine injection?

Use the injection right away if you notice:

• Shortness of breath, coughing, weak pulse, hives, throat tightness or trouble breathing.
• A combination of symptoms from different areas of your body, such as hives and swelling along with vomiting and diarrhea.

If you’re not sure if you need to use the injection, most allergists recommend using it. The benefits of using it outweigh the risks of using it when you don’t necessarily need it.

What other medicines can treat a shellfish allergy?

If you have mild symptoms, your healthcare provider may recommend an antihistamine. However, only epinephrine can treat the severe symptoms of anaphylaxis.

Does Benadryl help a shellfish allergy?

Yes, Benadryl® and other antihistamines can help with mild allergic reactions like itching skin or skin rash.

How can I avoid an allergic reaction to shellfish?

The only way to avoid the negative effects of shellfish is to avoid shellfish entirely.

How else can I lower my risk for an allergic reaction?

In addition to not eating shellfish, these precautions can help you stay safe:

• Try not to cook or touch shellfish: Particles can become airborne during cooking and cause an allergic reaction. While rare, it can still occur. Some people have a reaction to handling shellfish.
• Use caution in seafood restaurants: Even non-shellfish dishes prepared in seafood restaurants may contain shellfish. Restaurants often use the same cooking equipment (and often, the same frying oil) for shellfish and non-shellfish dishes, so there may be contamination.

What other foods might contain shellfish?

These food items may contain shellfish, as well, so avoid eating them:

• Bouillabaisse, cioppino and other seafood stews.
• Cuttlefish ink.
• Fish stock.
• Imitation fish.
• Seafood flavoring.
• Surimi.

Is a shellfish allergy dangerous?

Any food allergy can be dangerous. Even if you’ve only experienced mild allergic symptoms to a food, you can always potentially have a dangerous reaction to that same food. It’s smart to be careful and prepared. Always carry your epinephrine injection with you. Note the expiration date so you can get a new one before it expires.

Does a shellfish allergy go away?

Most people who have a shellfish allergy have it for life. It doesn’t go away over time.

How do I take care of myself if I have a shellfish allergy?

You can live a healthy, enjoyable, active life with a shellfish allergy. Take some precautions to keep yourself healthy and feeling your best:

• Know what you’re eating and drinking.
• Check label ingredients — even if it’s a product you’ve eaten safely before. Often, manufacturers change recipes. They may have added shellfish since the last time you ate the product.
• If your child is allergic, teach them not to accept food from friends.
• Be restaurant-safe: Ask detailed questions about ingredients and food preparation when you eat out.
• Wear your medical alert bracelet or carry an alert card with you.
• If your healthcare provider prescribed self-injectable epinephrine, carry it with you at all times. Make sure you have two doses available, as you may need to repeat the injection.

When should I see my healthcare provider?

Contact your healthcare provider if you notice any allergy symptoms after consuming shellfish. Even if your first reaction was mild, your second or third reaction could be severe. It’s best to be safe and have your provider test you for a shellfish allergy.

When should I go to the ER?

Go to your nearest emergency department if you have symptoms of anaphylaxis (like difficulty breathing and/or difficulty swallowing), or if you don’t get relief from using your injectable epinephrine.

What questions should I ask my healthcare provider?

It’s normal to have questions about shellfish allergies. Some questions you may want to ask your allergist include:

• What foods should I avoid?
• Am I allergic to all seafood?
• Can I touch shellfish? Or just not eat it?
• Would you recommend any additional testing?
• What do I do if I have an allergic reaction?
• How do I use my emergency epinephrine injector?

What shellfish are most allergenic?

Crustaceans like shrimp, lobster and crab tend to cause more allergic reactions. Of the crustaceans, shrimp causes the most allergies.

Why am I allergic to shellfish but not fish?

Shellfish allergies and fish allergies are different because they’re different animals. You may have a shellfish allergy but be able to eat fish (and vice versa). They’re both ocean animals, but fish have bones and fins, whereas a shellfish has a shell and no bones.

Is an allergy to shellfish related to an iodine allergy?

Shellfish allergies are sometimes confused with iodine allergies. That’s because shellfish often contain 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 to radiocontrast material.

A note from Cleveland Clinic

A shellfish allergy can be annoying. It can interfere with your life, especially if you enjoy eating seafood. It’s smart to take precautions and avoid shellfish, even if you only experience mild symptoms. By avoiding shellfish, you can almost eliminate the uncomfortable (and potentially life-threatening) risks of an allergic reaction. If you notice symptoms after eating shellfish, talk to your healthcare provider or allergist to get a diagnosis. Your provider will talk to you about how to best care for yourself and explain how to use an epinephrine auto-injector.