Shellfish, crustacea and mollusca are the common causes of food allergy and Octopus variabilis, a kind of mollusca is a favorite food in Oriental countries. There have been some reports of allergy to mollusca, but case reports of ana¬phylaxis due to octopus are rare. We report a case of anaphylaxis after eating raw octopus. A 52-year-old man visited the emergency department with complaints of generalized urticaria, dizziness, and loss of consciousness at one hour after eating one piece of raw octopus leg. The allergy skin test with octopus extract showed weakly positive response (A/H ratio 2+). When serum specific IgE, IgG1 and IgG4 antibodies to octopus extract were measured by ELISA, increased level of specific IgG4 was noted compared to normal healthy controls, and specific IgE and IgG1 antibodies were undetectable. Serum tryptase level by CAP system showed markedly elevated level (146 IU/ml). These findings suggest that octopus could induce an anaphylaxis as a manifestation of food allergy probably due to non-IgE mediated mast cell activation. (Korean J Asthma, Allergy Clin Immunol 2004;24:257260)