generally speaking people with wheat sensitivities are allergic to gluten. wheatgrass has virtually no gluten and most who are gluten intolerant do just fine with wheatgrass. however, its always best to test it out with a very small amount to begin with, if no reaction, then try a little larger amount.
spirulina, chlorella, algae, kelp, etc, are all gluten free and you shouldn't have any problems with them.