Allergies to seafood and shellfish are common in many people, causing itching, rashes, and facial swelling. And if not treated promptly, the allergy can be life-threatening.

Shellfish allergy is an abnormal response of the immune system to proteins in certain marine animals. Seafood in the shellfish category includes crustaceans and mollusks such as shrimp, crab, lobster, squid, oysters, scallops, and others.