Seafood is one of the common causes of food allergies to adults. The sea hare Aplysia kurodai is a marine mollusk which belongs to invertebrate gastropod that has been consumed as a food in Korea. Cases of acute toxic hepatitis after ingestion of sea hares have been reported, but few cases of allergic reactions to sea hare have been reported in the literature. A 33-year-old man was referred to our Emergency Department due to urticaria and periorbital/perioral swelling after eating sea hares. Approximately 10 years ago, he experienced similar allergic reactions to it. Skin prick and intradermal tests showed strong positive responses to crude sea hare allergen extract. He was diagnosed with food allergy to sea hares. We herein report the first case of sea hare allergy after ingestion. (Allergy Asthma Respir Dis 2016;4:61-64)