Foods to Avoid When You Have a Shellfish Allergy

If you're allergic to shellfish, you need to avoid all shellfish or risk a potentially severe allergic reaction, such as anaphylaxis. This may seem like a simple task if you think you only need to steer clear of obvious shellfish like lobster, shrimp, and clams.

But there are actually many other types of shellfish. You may not even immediately recognize some of them as shellfish. For example, you might not realize that sea urchins and octopuses are shellfish too. As a person with a shellfish allergy, you have to avoid all of them.

Shellfish are not the same type of creatures as fish. People with a shellfish allergy may be able to eat fish with no problem. And people with a fish allergy may be able to consume shellfish.

But to protect yourself, you need to know exactly what types of sea creatures qualify as "shellfish." You also need to know where they're typically found in meals, both in restaurants and at home.

This article is a comprehensive guide to shellfish. You will learn what foods contain shellfish and how you can protect yourself when you have a shellfish allergy.

Foods That Trigger Shellfish Allergies

Verywell / Brianna Gilmartin

Shellfish Types

Shellfish are divided into two families—mollusks and crustaceans. It's possible to be allergic to just one of these two types of shellfish. For example, you might be allergic to crustaceans but not mollusks.

However, most people who are allergic to one type actually are allergic to both. For this reason, don't eat any shellfish from either family without talking to your doctor about your allergy first.

Crustaceans
  • Crab

  • Crawfish (crayfish, crawdads)

  • Langoustines

  • Lobster

  • Prawns

  • Sea urchin

  • Shrimp

Mollusks
  • Abalone

  • Clams (quahogs)

  • Cockles

  • Limpets

  • Mussels

  • Octopus

  • Oysters

  • Scallops

  • Snails (escargot; both sea and land snails)

  • Squid (calamari)

  • Surimi (imitation shellfish, often found in sushi)

  • Whelks

Unfortunately, you can't trust food packaging to warn you about all shellfish. Food labeling laws in the United States only cover crustaceans, not mollusks. Only ingredients made from crustaceans must be identified on labels with an allergy warning. This can be a problem for people who have bad allergic reactions to mollusks.

Most food packaging will highlight (or at least list) mollusk ingredients. For this reason, you should easily be able to identify mollusk-containing foods.

For example, a jar of white clam sauce almost certainly will contain clams or clam juice. You'll know to steer clear of it. And fried calamari, also known as fried squid, will include calamari.

Make sure to read food labels carefully. When in doubt, don't eat the food you're not sure about.

Avoiding Shellfish in Restaurants

If you have a shellfish allergy, you'll need to be extremely careful when dining out. You may want to avoid seafood restaurants entirely. This is because people with severe shellfish allergies have had allergic reactions simply from breathing in allergens (allergy-triggering substances) from shellfish that are being steamed, fried, or boiled.

In fact, depending on the severity of your allergy, you should consider avoiding some types of restaurants and cuisines entirely. If you don't, you run a high risk of cross-contamination. These restaurants and cuisines include:

  • Chinese, Japanese, Thai, Vietnamese, or Malaysian foods, which often include a fish sauce made from shrimp or imitation shellfish
  • Cajun or Creole food, which frequently contains shrimp or other shellfish

Some restaurants may use shellfish stock as a flavoring or base for sauces or soups. Always tell your server or a manager about your allergy. Ask them if any items you're thinking about ordering contain shellfish.

Foods That Often Contain Shellfish

Shellfish is an ingredient in numerous recipes, although it may not always be obvious. Be on the lookout for these dishes and ingredients in restaurants. Also be careful when eating food prepared by friends or relatives:

  • Bouillabaisse (a French fish soup)
  • Ceviche (fish or shellfish in an acidic citrus marinade)
  • Cioppino (fish stew)
  • Clamato (a clam broth and tomato juice mixture sometimes used in Bloody Mary drinks)
  • Crevette (the French term for shrimp)
  • Scampi (contains lobster or shrimp)
  • Etouffée (Cajun crawfish dish)
  • Gumbo (fish and shellfish stew)
  • Paella (Spanish rice dish usually made with shrimp)
  • Jambalaya (Cajun rice dish often made with shrimp or crawfish)
  • Nam prik (Thai fish sauce)
  • Mam tom (Vietnamese fish sauce)

Non-Food Sources of Shellfish

When you have a severe shellfish allergy, you also need to be aware of potential non-food sources of the allergen. These can include:

  • Compost or fertilizers
  • Fish food
  • Pet food
  • HemCon bandages (a wound dressing made from shrimp shells)
  • Calcium supplements made from oyster shells or coral
  • Glucosamine
  • Omega-3 supplements (usually made from fish, but sometimes made from shellfish)

Summary

Shellfish allergy can cause severe symptoms. If you've been diagnosed with it, you'll need to carefully avoid all shellfish. This isn't always easy, since some food ingredients may not be immediately recognized as shellfish.

Carefully reading ingredient labels and understanding which sea animals are classified as shellfish can protect you from accidentally eating it. You may also need to avoid restaurants and certain cuisine that commonly use shellfish in recipes.

A Word From Verywell

If you're allergic to shellfish, you need to be extremely careful with the food you eat. Fortunately, shellfish can be easier to avoid than some other allergens. This is because they're an expensive ingredient. And they are usually not hidden in ingredient lists on food labels or restaurant menus.

If you have any questions about which foods you should avoid, ask your doctor to refer you to a dietitian who specializes in food allergy.

Frequently Asked Questions

  • Can you develop a shellfish allergy as an adult?

    Absolutely. In fact, about 60% of people with shellfish allergies experience their first symptoms in adulthood. One reason may simply be that they, like many children, never tried shellfish until they were older.

  • Can you be allergic to crab but not shrimp?

    Crab and shrimp are both crustaceans. If you're allergic to one crustacean, you're likely allergic to all of them. It's possible to be allergic to crustaceans such as shrimp and crab but not mollusks—clams, oysters, mussels, squid, and octopus.

  • Can a shellfish allergy go away?

    It's unlikely. In studies, even when people allergic to shellfish underwent a "challenge"—progressively eating larger amounts of shellfish under the supervision of an allergist to teach the immune system to not react to it—they were unlikely to eliminate the allergy.

  • What component of shellfish causes an allergic reaction?

    The primary allergen in shellfish is a protein called tropomyosin. Others include parvalbumin and arginine kinase. In all, there are around 20 individual proteins that are potential allergens in shellfish.

  • How long do shellfish allergy symptoms last?

    It depends on the severity of the reaction. Also, some people have a second wave of symptoms after the first one resolves, called a biphasic reaction, so it's advisable that someone who has a severe reaction to seafood be observed in a hospital for at least six hours. Keep in mind, too, that symptoms of seafood allergies don't always occur immediately: It could take several hours for them to develop.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Jeanette Bradley
Jeanette Bradley is a noted food allergy advocate and author of the cookbook, "Food Allergy Kitchen Wizardry: 125 Recipes for People with Allergies"