Conch is a gastropod, a very large marine snail, so it is shellfish in the mollusc sense rather than the crustacean sense. That matters on a label. EU rules require molluscs to be declared as their own allergen, but US labelling law only compels crustacean shellfish to be named, so conch can appear in a chowder or a fritter without a shellfish warning on the front of the pack. If your diagnosis is crustacean allergy, conch is a separate question for testing, not an automatic no and not an automatic yes.

It carries a real and repeatedly documented risk. The organism most often implicated is Vibrio parahaemolyticus, which occurs naturally in warm seawater and sits on the conch surface, so it is not a sign of a dirty kitchen. Bahamian authorities have issued public advisories urging people to avoid raw conch during case clusters. Washing the meat thoroughly in clean fresh running water removes much of the surface load, but the only preparation that removes the risk is cooking. If you are pregnant, immunocompromised or have liver disease, raw conch is not a reasonable gamble.

No, it grades borderline rather than moderate or high, and it is not graded as a histamine liberator. That puts conch at the gentler end of the shellfish range for anyone on a low-histamine plan, largely because conch is landed alive in the shell and usually frozen quickly rather than sitting on ice as picked meat. The forms that undo that advantage are the aged ones: long-marinated conch, conch that has been sitting dressed in a salad for hours, and leftovers reheated the next day.

The meat is, and it grades clean for gluten, but the two most common conch dishes are not. Cracked conch is pounded thin, dredged in seasoned wheat flour and fried, and conch fritters are lumps of conch in a wheat batter. Both usually come out of a fryer shared with other breaded items. Conch chowder is the safer route if the kitchen has not thickened it with a roux, and grilled or steamed conch keeps the clean profile the ingredient actually has.