Shrimp is a crustacean which is part of the shellfish family. There are two groups of shellfish: crustaceans (inclusive of shrimp, prawns, crab and lobster) and mollusks/bivalves (such as clams, mussels, oysters, scallops, octopus squid, abalone, snails). It is estimated that around 2% of the American population has allergies to shellfish. It is very individual on what the body tolerates. Some individuals can freely eat shrimp but have reactions to oysters. Best way to assess if you have any allergens is a food intolerance test and it can be geared specifically to shellfish.
