Crab & Eczema
Same allergen as shrimp (tropomyosin, 92–98% identical). If allergic to shrimp, assume crab allergy too. Hides in bisques, California rolls, and shared restaurant fryers.
4/5
Reaction Timeline
Crab triggers IgE-mediated shellfish allergy through tropomyosin — the same muscle protein that drives shrimp reactions — because crab tropomyosin (Cha f 1) shares 92–98% amino acid identity with shrimp's. Reactions are typically immediate: hives, swelling, throat tightening, and in severe cases anaphylaxis can occur within minutes to two hours of eating crab or even inhaling cooking vapours. There is no delayed 12–72 hour window typical of eczema food intolerances — crustacean allergy is fast and should be treated as a potential emergency. If you are allergic to shrimp, cross-reactivity with crab is near-universal.
How Much Is Needed To React?
Same as shrimp — trace amounts can trigger reactions. Surimi (imitation crab) is made from fish but may be processed on shared equipment with real crab.
Does Preparation Matter?
Tropomyosin is heat-stable. No cooking method reduces crab allergenicity. All forms — steamed, boiled, baked, fried — are equally allergenic. Crab shell handling can cause contact reactions. [1]
Also Watch Out For...
Shrimp — 92–98% tropomyosin homology [1]
Lobster — 92–98% tropomyosin homology [1]
House dust mite — ~80% tropomyosin homology [2]
Cockroach — tropomyosin cross-reactivity
Mollusks — ~14% clinical cross-reactivity
What To Use Instead
White fish (cod, sole) — no cross-reactivity with crustaceans
Chicken or turkey (for protein)
Jackfruit (pulled texture mimics crab in some recipes)
Lion's mane mushroom (seafood-like texture — note: mushrooms on trigger list)
Hidden Sources
Surimi/imitation crab (may contain real crab or be processed on shared lines)
Crab cakes and crab dip
Bisques and chowders
Sushi (California rolls, crab rangoon)
Bouillabaisse and cioppino
Shared fryer oil in restaurants
Chitin-based products
