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—it means you must steer clear of obvious shellfish like lobster, shrimp, and clams.

But there are actually many other types of shellfish, some of which you might not immediately recognize as shellfish. For example, you might not realize that sea urchins and octopus are shellfish. 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 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," and where they're typically found in meals, both in restaurants and at home. Read on for a comprehensive guide to shellfish.

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, crustaceans), but not the other (for example, mollusks).

However, most people who are allergic to one of these actually are allergic to both. Therefore, don't eat any shellfish from either family without talking to your healthcare provider about your allergy first.

  • Crab

  • Crawfish (crayfish, crawdads)

  • Langoustines

  • Lobster

  • Prawns

  • Sea urchin

  • Shrimp

  • 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. Therefore, only ingredients made from crustaceans must be identified on labels with an allergy warning. This can be problematic for people who have bad allergic reactions to mollusks.

However, most food packaging will highlight (or at least spell out) mollusk ingredients, so you should be able to identify mollusk-containing foods readily. For example, a jar of white clam sauce almost certainly will contain clams or clam juice, so you'll know to steer clear. And fried calamari (also known as fried squid) will include calamari.

Make sure to read food labels carefully, and when in doubt, don't eat the food in question.

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 since people with severe shellfish allergies have had allergic reactions simply from breathing in particles of allergens from shellfish that is being steamed, fried, or boiled.

In fact, depending on the severity of your allergy, you should consider avoiding some types of restaurants and cuisines because of the high risk of cross-contamination. These 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, and ask if any items you're considering 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 and 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)

A Word From Verywell

Shellfish allergy can cause severe symptoms. If you've been diagnosed with it, you'll need to carefully avoid all shellfish.

Fortunately, shellfish can be easier to avoid than some other allergens, since they're an expensive ingredient and therefore are likely to be celebrated, not hidden, in ingredient lists, on labels, and as part of restaurant menus.

If you have any questions about which foods you should avoid, ask your healthcare provider for a referral 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.

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