Seafood Allergy

Hello,
By searching on food allergy I gathered several good tips. I guess my question is on successfully communicating with a busy wait-person. I saw the recommendation to carry a laminated card stating my allergy: something like

Tengo una alergia a mariscos

Specifically, I have an allergy to the iodine found in shellfish like shrimp, prawn, and lobster. Fish (tuna, shark, even squid) are fine. So, is "mariscos" too broad of a term?

If we were chatting in COBOL or JAVA, I would be all set: but I have very limited Spanish skills.

Thank you for your comments.

Paul

Thank you for your responses.
Adding shells and other bits of shellfish is common practice in sauces and soups in the USA also. Fortunately, I recognize the early warning that it is present in food. I can push the plate away, drink more water and I will be okay.

Bringing my card will help me be more confortable but I will be careful.

Paul