Contact urticaria caused by heat-sensitive raw fish allergens

Patients allergic to fish usually present with skin reactions after handlin g raw fish. Less frequently, these reactions are seen without symptoms afte r oral intake, often in chefs and food handlers. We have attempted to expla in the skin selectivity of such reactions in a 36-year-old woman with conta ct urticaria after handling raw fish. We obtained aqueous extracts of raw a nd cooked fish (sole and hake) for in vivo (prick test) and in vitro (SDS-P AGE, IgE Immunoblot) tests. Prick-by-prick test, 20-min closed patch test, rub test with fresh and cooked fish (sole, hake and cod) and specific IgE ( CAP-system) to sole, cod and hake were performed. The strength of positive reaction to raw fish was greater than to cooked fish on both prick and pric k-by-prick testing. Rub tests showed positive responses only to raw fish. S pecific IgEs to sole (45 KU/l), hake (66.9 KU/l) and cod (18.7 KU/l) were o btained. IgE immunoblot recognized 3 antigens of 25, 48, 56 kDa in raw sole and 1 of 42 kDa in raw hake extracts. No IgE binding was observed with the cooked extracts or control sera. Our findings strongly suggest a Type-I hy persensitivity to fish. Immunoblot analyses demonstrated a loss of specific IgE binding to cooked extracts. We have reported a case of contact urticar ia caused by heat-sensitive raw-fish allergens in a patient who probably be came sensitized via the cutaneous route.