I am allergic to all crustaceans. The symptoms are swelling lips and throat, and an itchy rash if there is skin exposure. It came on in my late 30s, so unfortunately I know I like the things! Probably started by a crustacean's haemolymph getting into a cut on my hands when shelling prawns. Being sick sounds more like exposure to an iffy lobster.
It's actually a fairly serious matter for me - my wife is from Hong Kong, where a usual seasoning in food is dried shrimp! So I have to be very careful when in Hong Kong.