Crab

 
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Code: f23
Latin name: Cancer pagurus
Source material: Boiled crab meat
Family: Cancridae
Crab is a potent allergen, sometimes causing dramatic manifestations, such as anaphylaxis.

Allergen Exposure

Boiled meat.
 
Unexpected exposure
Dust and waste water in factories producing seafood products.

Potential Cross-Reactivity

Common major allergens have been identified in crab, crayfish, shrimp and lobster.

Clinical Experience

IgE-mediated reactions
Crab is a potent allergen, sometimes causing dramatic manifestations. It may also be considered an occupational allergen for workers in the food industry.
 
Other reactions
Seafood may contain high levels of histamine.
 
Review
In all, there are about 45,000 crab species living in the seven oceans, in fresh water and on land. These 10-footed creatures are divided into about 30 families of the order Crustaceae. Various species are commercially processed according to the quality and quantity of meat. Snow crabs, King crabs and Dungeness freeze well. Blue crab from the Atlantic and Gulf of Mexico are more often canned. The soft-shelled crabs are harvested immediately after molting. Modern food technology has designed crab-look-and-taste-alikes (surimi), which are actually mixtures of flavorings, other less expensive fish and chemicals to give the characteristic crab color.
 
Clinical experience
Crab is a potent allergen, sometimes causing dramatic manifestations. Yunginger et al. (1) reported a fatal IgE-mediated anaphylaxis after ingestion of crab. It may also be considered an occupational allergen for factory workers who inhale dust from seafoods and come into contact with the water in which the food was cooked (2-4). Lehrer (3) found cross-reactivity between crab, crayfish, shrimp and lobster, and common major allergens have been identified in shrimp, lobster and crayfish (5).
 
A survey of food allergy in France showed crab to be responsible for 34% of the recorded reactions (6).

References

  1. Yunginger, JW; Sweeney, K G; Sturner, WQ; Giannandrea, LA; Teigland, JD; Bray, M; Benson, PA; York, JA; Biedrzycki, L; Squillace, DL; Helm, RM. Fatal food-induced. anaphylaxis. JAMA; 1988; 260: 1450-1452.
  2. Cartier, A; Malo, J-L; Ghezzo, H; McCants, M; Lehrer, S. IgE sensitization in snow-crab processing workers. J Allergy Clin Immunol; 1986; 78: 344-348.
    Lehrer, SB. Hypersensitivity reactions in seafood workers. Allergy Proc; 1990; 11(2):67-70.
  3. Malo, JL; Chretien, P; McCants, M; Lehrer, S. Detection of snow-crab antigens by air sampling of a snow-crab production plant. Clin Exp Allergy; 1997; 27: 75-78.
  4. Daul, CB; Slattery, M; Morgan, JE; Lehrer, SB. Identification of a common major crustacea allergen. J Allergy Clin Immunol; 1992; 89: 194.
  5. Andre, F; Andre, C; Colin, L; Cacaraci, F; Cavagna, S. Role of new allergens and of allergen consumption in the increased incidence of food sensitization in France. Toxicology; 1994; 93: 77-83.

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.