Mollusks and crustaceans contain proteins that some people are allergic to. These foods can include crab, shrimp, lobster, oysters, scallops, clams, mussels.
The crustaceans (crab, shrimp, and lobster) are the more commonly allergenic shellfish, and packaged foods containing them are required to be labeled as “shellfish” in the U.S. Allergies to mollusks are less common, but they do occur.
Some people can even be allergic to the vapors created by cooking shellfish, so you may not want to keep out of the kitchen when that’s happening. Shellfish allergies are usually lifelong.