Among the rare foods capable of producing food allergies is the snail (Helix terrestre). The snail is a delicacy eaten in Spain, France and Portugal. This study presents the findings of an allergic study of 10 patients with this infrequent food allergy during the past 10 years. The shock organ in the majority (80%) of these patients was the bronchial tree. Six of them did not have any digestive or skin symptoms which are usually seen in cases of food allergy. All patients manifested the symptomatology after ingestion of Helix terrestre. Two also had reactions after eating Patella vulgata (limpet). The snail and the limpet are within the phylogenetic line of molluscs, i.e. of gastropods. All patients tolerated the ingestion of cephalopods and bivalves which belong to two other phylogenetic lines. Skin tests to seafoods (squids, prawns, lobsters and clams) were negative for all patients. This suggests that the sensitizing antigen is probably a protein found only in gastropod molluscs. Skin tests along with the histamine release test were valid diagnostic methods for this food allergy. The limited bibliography on this subject is probably due to the fact that the consumption of snails as well as limpets is limited to specific geographical areas.