Shellfish allergy
Shellfish covers two very different groups: crustaceans (shrimp, crab, lobster) and molluscs (clams, mussels, squid). Crustacean allergy is the more common and usually the more severe, and the two groups cross-react less than people assume. Each guide below covers one shellfish; the cross-reactivity guides explain what genuinely travels together.
Crustaceans
Molluscs
How these foods cross-react
If your child reacts to one, this is what else genuinely travels with it, and the shared-protein reason why.
- Food familyCrustacean shellfish cross-reactivityIf you react to one crustacean, you usually react to them all. Why shrimp, crab, lobster, and crayfish are managed as one group, how crustacean shellfish is labeled, why molluscs are a separate and less predictable question, and why fish is not shellfish. Cited.
- Food familyMollusc cross-reactivityMollusc cross-reactivity is moderate and uneven, not all-or-nothing. Bivalves, cephalopods, and gastropods, which molluscs cross-react, and the big one: molluscs are not a US major allergen, so they often go unlabeled. How to read the label. Cited.
- Shared proteinTropomyosin: shellfish, dust mite, and insect cross-reactivityTropomyosin is the shared muscle protein behind shellfish cross-reactivity. Why one crustacean predicts the others, why molluscs are less predictable, why dust mites are linked, and why fish is not shellfish. Cited.