Where crab hides

By Symon, Every Label · June 30, 2026

Crab is one of the easier allergens to find on a label and one of the easier ones to miss in real food. Easy to find, because crab is crustacean shellfish, a major allergen in the US, the EU, and the UK, so a packaged food has to declare it by name. Easy to miss, because it turns up in seafood stocks and seasoning blends that never say “crab,” in mixed-seafood dishes where it is one item among many, and in one product whose whole name is built to confuse you: imitation crab. This page is the crab label-reading guide. The good news is that the words are few and they repeat, so once you know the shape of them they start jumping out.

Where a fact below is clinical, it carries its source. None of it is a substitute for your allergist. This is the deep version of the hidden-sources summary that will sit on the main crab page; that page is the overview, this is the full scan.

Scan this first

If you read nothing else, read this box. These are the words that mean crab, the one product that traps people in two directions, and the places it hides that are easy to miss.

The words that mean crab on a label: crab, crabmeat, and any named crab (dungeness, snow, blue, king, mud crab) all mean crab. “Crustacean shellfish” on a label or a “contains” line means crab’s group. Surimi and “imitation crab” (sometimes spelled “krab”) are a special case, below (acaai 2024, falcpa).

The one trap, both ways: “imitation crab” or “krab” is usually made from fish (pollock), not crab, so it is a risk for a fish allergy even though the name says crab. But it is also commonly flavored with crab or crustacean extract and made on shared crustacean equipment, so it is not reliably crab-free either. Do not read “imitation” as “free of.” Scan the full ingredient list and ask, for crab and for fish (acaai 2024).

Easy-to-miss hiding places: seafood or shellfish stock, bisque, she-crab soup, “seafood flavoring,” “seafood extract,” and Old Bay-style seafood seasoning routinely carry crab or other crustacean protein, and a restaurant stock or seasoning has no ingredient list at all, so the question goes to a person (acaai 2024).

When a term is unclear and the label will not tell you, that is a reason to ask, not a reason to assume it is safe.

Where crab hides, by category

Crab is declared on packaged food, so most of the work here is in the places where the ingredient list is thin, generic, or absent.

Processed and packaged foods under non-obvious names. Crab and undifferentiated crustacean protein show up in seafood stock and bisque bases, “seafood flavoring” and “seafood extract,” shellfish-derived seasoning and flavor blends (Old Bay-style seasonings), some Asian condiments and broth bases, and crab paste used in Asian cooking. The tell is in the lexicon below: crab, crabmeat, crustacean shellfish, and the surimi terms are the ones that mean crab, and “seafood extract” or “seafood flavoring” are check-it terms (acaai 2024). On a US packaged label, deliberate crustacean is declared, so the back of the package is reliable for what was added on purpose; the gap is the generic wording and everything that is not packaged.

Surimi and imitation crab are their own category. Surimi, sold as “imitation crab,” “imitation crabmeat,” or “krab,” is the central trap of this page. It is usually a fish (pollock) product, so it is a fish risk under a crab name; and it is commonly crab-flavored or crustacean-flavored and processed on shared crustacean equipment, so it is also a crab risk. It turns up in California rolls and other sushi, seafood salads, dips, and seafood medleys. Treat it as a scan-and-ask item in both directions and never as a safe word (acaai 2024).

Cuisines and restaurant dishes. Crab is built into seafood cooking: shellfish or seafood stock, bisque, she-crab soup, bouillabaisse and other seafood soups, XO sauce, seafood boils, crab dips, and mixed-seafood medleys, platters, and paella. A restaurant stock or a house seasoning has no label, so the ingredient list cannot help you and the question goes to the kitchen. Two specifics worth naming: XO sauce and many seafood medleys also carry mollusc (dried scallop), which US labels are not required to declare at all, so a seafood dish can hide both crab and a mollusc; and shared fryer oil, a shared wok, and shared prep surfaces add crab by cross-contact even to a dish that is not itself crab (acaai 2024). A chef card that names crab and “crustacean shellfish” plainly, and asks about shared fryers and woks, does more than a spoken order across a loud kitchen.

A note on cooking: heat does not make crab safe. Unlike some allergens, crab is not reduced by cooking. The main crab allergen, tropomyosin, is heat-stable and survives digestion, so boiled, steamed, canned, and dried crab keep the allergy risk. This is here because “it was cooked” is a common false reassurance; for crab it does not hold.

Non-food: a steam-and-aerosol route, and one medication question (kept in proportion). Crab has a real inhalation route that most food allergens do not. Crab-processing aerosol and the air around live-tank seafood markets and seafood cooking can carry crab protein in the steam, which is an exposure for a sensitized person in that setting, separate from eating it (cartier). Separately, if your child is a crab-allergic candidate for allergy shots or drops for dust-mite allergy (immunotherapy for asthma or hay fever), there is a tropomyosin overlap between dust mite and shellfish worth raising first: ask the allergist about tropomyosin or Der p 10 testing and a shellfish-and-snail conversation before starting. That is a flag-it-and-ask, not a reason to start or stop any treatment on your own, and the detail lives on the cross-reactivity pages (see Related pages).

Cross-contact and shared equipment. Shared fryer oil, a shared wok or grill, shared seafood-market surfaces, and mixed-seafood platters are frequent incidental crab sources even when the item you ordered is not crab. This is the route that the ingredient list cannot warn you about.

The label lexicon

This is the core of the page. These are the exact terms on an ingredient list or a menu that mean crab, or that mean check-it. Learn the shape of them once.

Always crab, or crab’s group (avoid):

• crab, crabmeat, crab meat, crab paste
• named crabs: dungeness crab, snow crab, blue crab, king crab, mud crab
• “crustacean shellfish” (the FALCPA category term; means crab and its group)
• scientific names you may see on specialty or imported products: Callinectes, Cancer, Portunus, Scylla, Brachyura

(acaai 2024, falcpa.)

Slow-down terms (check, do not assume):

• surimi, “imitation crab,” “imitation crabmeat,” “krab”: usually fish (pollock) but commonly crab-flavored and shared-equipment; a risk for crab AND fish, scan and ask (acaai 2024)
• “seafood extract,” “seafood flavoring,” “shellfish stock,” “fish stock with shellfish”: can carry crab or undifferentiated crustacean protein (acaai 2024)
• “natural flavor” or “natural flavoring”: can mask crustacean flavoring, especially in non-EU markets where transparency varies
• “fish sauce,” “shrimp paste” (belacan), XO sauce, oyster sauce in a seafood blend: seafood condiments that may carry crustacean

Usually a false alarm (worth knowing so you do not over-restrict):

• (none cleared for crab.) The reassurance-shaped corrections people reach for here, that a shellfish allergy does not mean an iodine-contrast or glucosamine problem, are real and useful but they are not label-reading facts, and they are covered on the cross-reactivity pages, not here. This list is deliberately empty rather than filled with an uncleared reassurance.

The labeling-law reality

This is the highest-value insight on the page. For crab, the ingredient list is mostly on your side. The problem is everything around it.

Crab must be declared by name. Crab is crustacean shellfish, one of the major food allergens under the US Food Allergen Labeling and Consumer Protection Act (FALCPA), so a packaged food has to declare crustacean shellfish somewhere on the label, either in the ingredient list (naming the species, for example “crab”) or in a separate “contains” statement (falcpa, fda 2024). The EU and the UK require crustacean declaration too, under their allergen rules (eu 1169). So for a packaged, labeled food, the ingredient list is reliable: if crab is a deliberate ingredient, the law says it has to be there for you to find.

The gap is everything the rule does not cover. Four places the must-declare rule does not protect you:

• Molluscs are a separate allergen, and the US does not require them on the label. This is the big one for seafood. Crustaceans (crab, shrimp, lobster, crayfish) are a US major allergen and are declared. Molluscs (clam, oyster, scallop, mussel, squid, octopus) are NOT a US major allergen, so a US packaged label is not required to name them, and a mollusc can sit unlabeled inside “seafood” or “natural flavoring.” A seafood dish or sauce can therefore hide a mollusc even when the crustacean is declared, so a crab-allergic reader who also reacts to molluscs needs a separate scan for them. The EU and the UK do require molluscs to be declared, which closes this gap abroad (falcpa, eu 1169).
• Unpackaged and restaurant food. A seafood counter, a sushi bar, a restaurant kitchen, a deli salad, and a bulk seafood seasoning are not covered by packaged-food labeling the same way. There is no ingredient list to read, so the question goes to a person, and a chef card beats a spoken order.
• Voluntary, unregulated wording. “May contain crustaceans,” “made in a facility that processes shellfish,” and “processed on shared equipment with crustacean shellfish” are voluntary precautionary statements. They are not regulated and not a reliable measure of how much risk is actually present (falcpa). How strictly you treat them is a personal call along a spectrum, weighing a real but variable cross-contact risk against ruling out a large part of the seafood and prepared-food aisle. This page will not pick that threshold for you.
• Generic wording on the label itself. “Seafood flavoring,” “seafood extract,” and “natural flavoring” can carry crustacean protein and do not always spell out the species, especially on imported products and in non-EU markets. Treat them as check-it terms and call the manufacturer when the answer is not on the package.

What is not a hidden source

Over-restricting has a cost too: it shrinks an already-small safe list and wears a family down. So it is worth saying plainly what does not need avoiding, but only where that is genuinely cleared.

For crab, that list is empty here, on purpose. The reassurances people reach for, that a shellfish allergy is not an iodine or CT-contrast problem, that shellfish-derived glucosamine may be tolerated, that molluscs may be fine if you only react to crab, that cooking makes crab safer, are either introduction-risk questions for your allergist or are covered on the cross-reactivity pages, not label-reading facts for this page. Two of them are worth a direct word: cooking does NOT make crab safe (the allergen is heat-stable, see above), and the iodine and glucosamine questions are real and mostly reassuring but they belong with the cross-reactivity content and your allergist, not here. This page holds the line on avoidance and sends the reassurance questions where they belong.

How to act on this

The skill is a routine, and it gets fast.

1. Scan the ingredient list, every time, every purchase. Formulations change without notice, so a product that was safe last month can change. Look for the lexicon words above, and for the surimi and “seafood flavoring” terms, not just the word “crab.”
2. Treat surimi and “imitation crab” as scan-and-ask, both ways. It is a fish product and a possible crab source at once. Read the full list; where there is no list, ask. The answer matters for crab and for fish.
3. Scan separately for molluscs. US labels are not required to name clam, oyster, scallop, mussel, squid, or octopus, so if you avoid molluscs too, read the full ingredient list and ask, do not rely on a “contains” line.
4. Decide your precautionary-label rule with your allergist. “May contain shellfish” is a personal-threshold call; make it once, deliberately, rather than agonizing per product.
5. Use a chef card for unpackaged food. Name crab and “crustacean shellfish” in writing, and ask specifically about shared fryers, shared woks, seafood stock, and surimi in salads and rolls.
6. Call the manufacturer when a term is unclear. “Seafood flavoring” or “natural flavoring” with no species named is a reason to call, not a reason to assume.

Related pages on this site

• Crab allergy: the main profile (the hub this page expands on)
• Crustacean cross-reactivity: if you react to crab, what about shrimp, lobster, and crayfish? (owns the rates and the “treat the others as high-risk” question)
• Shellfish, iodine, and glucosamine: the myths, sorted (owns the iodine-contrast and glucosamine corrections)
• Crab and dust-mite immunotherapy: the tropomyosin overlap (owns the mite-immunotherapy pre-screen)
• Reading restaurant menus with a shellfish allergy
• Crab and shellfish recalls

These companion pages are being written and will be linked here as each one goes live.

Frequently asked questions

Is imitation crab safe for a crab allergy?

Do not assume so. “Imitation crab” or “krab” is usually made from fish (pollock), but it is commonly flavored with crab or crustacean extract and made on shared crustacean equipment, so it is not reliably crab-free (acaai 2024). It is also a fish product, so it is a risk for a fish allergy even though the name says crab. Scan the full ingredient list and ask, for crab and for fish. Never read “imitation” as “free of.”

What words on a label mean crab?

Crab, crabmeat, crab paste, and any named crab (dungeness, snow, blue, king, mud crab) all mean crab. “Crustacean shellfish” on a label or a “contains” line means crab’s group (falcpa, acaai 2024). “Surimi,” “imitation crab,” “seafood flavoring,” “seafood extract,” and “shellfish stock” are check-it terms that can carry crab or other crustacean protein.

Does cooking make crab safe to eat?

No. The main crab allergen, tropomyosin, is heat-stable and survives digestion, so boiled, steamed, canned, and dried crab keep the allergy risk. “It was cooked” is not a reason to treat crab as safe.

My child reacts to crab. Do US labels warn about clams and oysters too?

Not necessarily. Crustaceans (crab, shrimp, lobster, crayfish) are a US major allergen and must be declared. Molluscs (clam, oyster, scallop, mussel, squid, octopus) are NOT a US major allergen, so a US label is not required to name them, and a mollusc can sit unlabeled inside “seafood” or “natural flavoring” (falcpa). If you avoid molluscs too, scan the full ingredient list and ask. Whether a crab allergy means you also need to avoid molluscs is a separate, cross-reactivity question for your allergist (see Related pages).

Can crab be in the air, not just in food?

For some people, yes. Crab-processing aerosol and the steam around seafood cooking and live-tank seafood markets can carry crab protein, which is an exposure for a sensitized person in that setting, separate from eating it (cartier). If that applies to your child, raise it with your allergist; it is a known occupational and market-air route for crab.

References and medical review

This page is pending independent medical review; the note at the top of the page applies until a reviewer is assigned. The references below resolve every in-body citation. The hidden-source and labeling claims (shellfish stock and seasoning carriers, the surimi double-trap, and the mollusc labeling gap) are drawn from the project’s verified cross-reactivity and hidden-source floor, each carrying its own source there.

1. American College of Allergy, Asthma and Immunology (ACAAI). Shellfish Allergy. (Crustacean hidden sources: seafood flavoring, e.g. crab or clam extract; fish stock; sushi and surimi; crustacean shellfish is a major allergen, molluscs are not.) 2024. https://acaai.org/allergies/allergic-conditions/food/shellfish/
2. Food Allergen Labeling and Consumer Protection Act of 2004 (FALCPA), Public Law 108-282, Title II (crustacean shellfish a major allergen; molluscs not). https://www.fda.gov/food/food-allergensgluten-free-guidance-documents-regulatory-information/food-allergen-labeling-and-consumer-protection-act-2004-falcpa
3. US FDA. Food Allergies (major food allergens; crustacean shellfish declared, molluscs not; voluntary precautionary statements). 2024. https://www.fda.gov/food/nutrition-food-labeling-and-critical-foods/food-allergies
4. Regulation (EU) No 1169/2011 (Annex II allergens, including crustaceans and molluscs as separate listed allergens). https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32011R1169
5. Cartier A, et al. Occupational asthma in snow crab-processing workers (the classic crustacean-processing-aerosol disease; cited for the steam and aerosol inhalation route). J Allergy Clin Immunol. 1984. https://doi.org/10.1016/0091-6749(84)90256-2
6. The crab hidden-source floor resolves to the project’s verified floor: shellfish stock, bouillabaisse, XO sauce, and shrimp-paste seasonings as crustacean carriers, the “crustacean is declared on packaged food but restaurant stocks and seasonings are unlabeled, so ask” frame, and the XO-sauce and seafood-medley mollusc (scallop) note. The crustacean cross-reactivity rates and the iodine and glucosamine corrections are held to the cross-reactivity pages and are not restated here.