I Recently Developed An Allergy To Hard Shell Crabs As

I recently developed an allergy to hard shell crabs as well as canned tuna. Both have resulted in a trip to the ER for treatment of anaphylactic shock. However; I am still able to eat Alaskan king crab legs. I am wondering then, if I am truly allergic to shell fish or just a component of the hard shell crabs and tuna since I am able to eat the crab legs at will without reaction.