What is a shellfish allergy?

 
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Shellfish allergies are among the most common food allergies and can be quite severe. Shellfish encompass marine animals with shells such as shrimp, lobster and crab, as well as mollusks like scallops and squid. Some people are allergic to all shellfish, but others are only allergic to certain species.

The two types of shellfish:

  • Crustaceans with a hard exoskeleton, such as crabs, crayfish, lobster, shrimp, prawn

  • Mollusks with soft bodies, such as clams, oysters, mussels, scallops, squid, snails, octopus

Allergies to crab, lobster and shrimp are the most common and reactions to crustaceans tend to be more severe, sending more people to the emergency room than any other allergen. Finned fish and shellfish are not related families of food, so being allergic to shellfish does not necessarily mean that one also needs to avoid fish.

Contrary to popular belief, those with fish allergies do not need to avoid iodine and radiocontrast material in medical tests, as there is no relation between iodine and fish allergies.


When are shellfish allergies discovered?

Unlike other food allergies that impact babies and young children, shellfish allergies typically do not develop until later in childhood, adolescence or adulthood. Around 60% of people with a shellfish allergy experienced their first allergic reaction as adults. 


How to avoid shellfish

The only way to prevent an allergic reaction is to avoid consuming shellfish. Read food labels carefully for your allergen. Because shellfish is one of the Top 8 allergens, the federal government requires that all packaged food products clearly list them as an ingredient. Learn how to read a food label for shellfish ingredients before consuming packaged food, and be sure to always check for precautionary “may contain” statements with cross-contamination warnings. Note that these regulations don’t apply to mollusks such as clams, oysters and scallops.

When dining out in restaurants, always check to ensure that the pan, oil, or utensils used to prepare your meal weren’t cross-contaminated with other dishes containing shellfish. Consider avoiding eating at seafood restaurants as there is a high risk of cross-contact. Some people react after touching shellfish or inhaling the steam from cooking shellfish.


Shellfish can often be found in:

  • Asian restaurants

  • Bouillabaisse

  • Cuttlefish ink

  • Glucosamine

  • Fish stock

  • Seafood flavoring (e.g., crab or clam extract)

  • Surimi (imitation crab meat)

  • Sushi

Foods to avoid:

  • Fish stock

  • Fish sauce

  • Seafood flavoring

  • Gumbo

  • Dim sum

Alternative names for shellfish:

  • Barnacle

  • Crab (Castanea sativa)

  • Crawfish (crawdad, crayfish, ecrevisse)

  • Krill

  • Lobster (langouste, langoustine, Moreton bay bugs, scampi, tomalley, Homarus americanus)

  • Prawns

  • Shrimp (crevette, scampi)

  • Abalone

  • Clams (cherrystone, geoduck, littleneck, pismo, quahog, steamers)

  • Cockle

  • Cuttlefish

  • Limpet (lapas, opihi)

  • Mussels

  • Octopus

  • Oysters

  • Periwinkle

  • Sea cucumber

  • Sea urchin

  • Scallops

  • Snails (escargot)

  • Squid (calamari, Todarodes pacificus)

  • Whelk (Turban shell)

Non-food products that could have shellfish:

  • Pet food

Discover more!

Learn how to order in a restaurant with a shellfish allergy

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