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Thanks for all the responses.

Well, out of nearly 100 responses, all but one said that shellfish is fine UNLESS you have DH or obviously a basic shellfish allergy to begin with.

One other person said that you should avoid shellfish anyway because of the high mercury content.

Here is one persons response - quite detailed:
Those celiacs WITH DH MAY experience outbreaks from iodine in shellfish & other sources--seafood, sea salt, seaweed products (emulsifiers) as well as vitamins and iodized salt, because it can trigger an inflammatory responses in the IgA deposits found in the skin.

Should be okay for other celiacs, as along as they are not   allergic.

Shellfish is one of the top 8 things (also includes wheat, milk, soy, corn, peanuts, tree nuts, that causes 90% of all allergies.

Thanks again
Teresa
NJ

*Please provide references to back up claims of a product being GF or not GF*