Shellfish Allergy

Shellfish allergy is a reaction to crustaceans such as shrimp, crab and lobster, or to mollusks such as clams and oysters. U.S. labels must name crustacean shellfish by type; mollusks are not a major allergen.

  • Food safety
  • Allergens & labeling

Shellfish come in two groups. Crustaceans include shrimp, prawns, crab, lobster, crawfish and krill; mollusks include clams, mussels, oysters, scallops, squid, octopus and snails. Under U.S. law only crustacean shellfish count as a major food allergen, and labels must name the specific kind, such as crab or shrimp. Mollusks are not covered by allergen labeling rules, so FARE warns they can show up in foods unexpectedly. The main allergen is tropomyosin, a muscle protein; iodine is not the cause. Shrimp is the most common shellfish allergen in both children and adults.

FARE estimates 8.4 million Americans have shellfish allergy, the highest count of any food in its figures. About 60% of people with it have their first reaction as adults, and it is usually lifelong. Very small amounts can trigger anaphylaxis, and shellfish protein can even travel in cooking steam. For bakers, the main risks are shared kitchens and ingredients that hide shellfish, such as seafood flavorings, fish stock, surimi and glucosamine.

Key facts

Estimated Americans affected
8.4 million
First reaction in adulthood
About 60% of people with it
Major allergen under U.S. law
Crustaceans yes; mollusks no
Main allergen protein
Tropomyosin

In a bakery or commercial kitchen

  • Name the crustacean in both the ingredient list and the “Contains” statement, for example “Contains: shrimp”
  • Keep savory seafood items, such as crab cakes or shrimp puffs, on separate equipment, trays and racks
  • Review seasonings and flavor bases for seafood extracts, fish sauce, fish stock, or crab and clam flavorings
  • Avoid steaming or boiling shellfish near bakery prep areas, since shellfish protein can travel in steam

For home and cottage bakers

  • Ask guests about shellfish allergy every time; FARE notes many people have their first reaction as adults
  • Use separate platters and serving utensils for desserts when shellfish dishes share the table
  • Check savory mixes and seasonings for crustacean names such as shrimp, crab, lobster or krill

Related entries

Sources

Written by VanillaGoods in our own words from these sources. Last reviewed October 17, 2026.

  1. Questions and Answers Regarding Food Allergens, Including the Food Allergen Labeling Requirements of the Federal Food, Drug, and Cosmetic Act (Edition 5): Guidance for Industry, U.S. Food and Drug Administration
  2. Food Allergies: What You Need to Know, U.S. Food and Drug Administration
  3. Shellfish Allergy, Food Allergy Research & Education (FARE)
  4. Facts and Statistics, Food Allergy Research & Education (FARE)