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Navigating Allergies and Food Sensitivities

Shellfish Allergies

Shellfish Allergy Info

The prevalence of shellfish allergy in the general population is 2.0 percent and represents the most common form of food allergy in adults.1

Shellfish include marine animals with shells, such as clams, lobster and shrimp, as well as octopus and squid. Shellfish and finned fish do not come from related families of foods, so being allergic to one does not mean that you will not be able to tolerate the other.2 

There are two types of shellfish, and each kind contains different allergy-causing proteins.3

Crustaceans include:

shellfish free

  • crabs
  • lobster
  • crayfish
  • shrimp
  • prawns
  • Langoustines
  • Sea Urchin
Mollusks include:
  • bivalves, such as clams, mussels, oysters and scallops
  • gastropods, such as limpets, periwinkles, snails (escargot) and abalone
  • cephalopods, such as squid, cuttlefish and octopuses

Although these two groups are fairly distant biological relatives, there is a high rate of allergic cross-reactivity between the two. So, many people who are allergic to any shellfish are advised to avoid all shellfish.2,3

Shrimp is the considered the most allergenic.3

Shellfish Allergies and Dietary Supplements:
Glucosamine, a dietary supplement sometimes recommended for patients with arthritis, is often made from the shells of crustaceans. The proteins that are most likely to cause food allergies are not found in the shell, and recent studies have indicated that glucosamine is safe for people with shellfish allergies; however, if you are concerned, you can try vegetarian glucosamine.2

Coral calcium, which is obtained from ocean coral reefs, can trigger allergic reactions, such as hives, breathing problems and swelling, in people with shellfish allergies. 2

Another potential source of shellfish allergens is Omega-3 supplements, which are often made from seafood. The most common source used to manufacture these is fish (mostly cod liver), but check ingredients on the label before you take these.3

Shellfish Allergies and Iodine:
Although certain shellfish are rich in iodine, there is no evidence that shellfish allergies raise the risk of an iodine allergy, or that people with shellfish allergies need to take precautions to avoid iodine when undergoing medical tests. Iodine is not related to the protein that causes shellfish allergies.3

Shellfish and Labeling Laws:
Because shellfish are one of the eight most common allergens in the United States, they are covered by FALCPA (the FDA’s Food Allergy Labeling and Consumer Protection Act). This requires that the presence of shellfish be listed on labels in clear English, either in bold type or following the list of ingredients after the word "Contains." However, FALCPA only refers to crustaceans, and not to mollusks.

Compared to other allergens, shellfish is not usually a “hidden” ingredient and is relatively easy to identify and avoid. Shellfish is sometimes found in Worcestershire sauce, salad dressings, and other prepared sauces. Be aware that surimi (imitation shellfish) often contains shellfish extracts for flavoring and is often unsuitable for allergies, so check labels.

Menu terms that imply a particularly high likelihood of shellfish include:4

  • Bouillabaisse (a French fish soup)
  • Cioppino
  • A L’Americaine (a French sauce often served with lobster or other shellfish)
  • Crevette (the French term for shrimp)
  • Scampi
  • Ceviche (fish or shellfish "cooked" by marinating in an acidic citrus-based marinade)
  • Etouffée
  • Gumbo
  • Jambalaya



NIH: National Institute of Allergy and Infectious Diseases

Food Allergy.


Food Allergy Initiative.

Shellfish Allergy.


Mayo Clinic.

Shellfish Allergy.

4 Food Allergies.

Shellfish Allergy: What You Need to Know.