COMMON ALLERGENS → Shellfish & Fish

COMMON ALLERGENS → Shellfish & Fish

Gerbs Allergy Hub - Fish & Shellfish Allergens


Those allergic to shellfish are more likely to be allergic to other invertebrates like dust mites and insects.


  • In terms of allergies, the three most relevant seafood groups are fish, crustacean, and mollusks. Crustaceans and mollusks are most often referred to as shellfish and are invertebrates. Crustaceans include crab, shrimp, and lobster while mollusks include many creatures ranging from mussels and clams to squid and octopus! Crustaceans appear to incite the most allergic reactions, compared to mollusks.
  • Shellfish and fish allergies are one of the most common causes of life-threatening anaphylaxis, and are typically lifelong allergies.
  • Reactions to shellfish and fish typically occurs immediately after direct ingestion, skin contact, or inhalation of cooking vapors (in some cases). Reactions commonly include anaphylaxis (especially for shellfish), itching/swelling of lips, throat, and mouth, vomiting, and diarrhea.
  • There appears to be cross-reactivity between mollusks and crustaceans but little cross-reactivity between shellfish and fish. So, shellfish and fish allergies are separate; those who are allergic to fish may not need to avoid shellfish, and vice versa.
  • Salmon, tuna, and halibut are the most common fish allergies.

Common (and Hidden!) Sources

  • Fish: any finned fish
  • Mollusks: snails, clams, squid, octopus, mussels, oysters, scallops
  • Crustacean: crab, lobster (langoustine, langouste), shrimp, prawn, crayfish (crawfish)
  • Commonly used in: fish stock/sauce, surimi, imitation crab meat, glucosamine, bouillabaisse, sushi, scampi.

1. Moonesinghe H, Mackenzie H, Venter C, et al. Prevalence of fish and shellfish allergy: A systematic review. Ann Allergy Asthma Immunol. 2016;117(3):264-272.e4. doi:10.1016/j.anai.2016.07.015.
2. Shellfish allergy – Lopata – 2010 – Clinical & Experimental Allergy – Wiley Online Library. Accessed September 21, 2017.
3. Sharp MF, Lopata AL. Fish Allergy: In Review. Clin Rev Allergy Immunol. 2014;46(3):258-271. doi:10.1007/s12016-013-8363-1.