Here I've found one reference to casein used in the wax on apples. It sounds like casein is more usually added to wax on citrus fruit rather than on apples. But at least one company puts casein in apple wax. Here's the link: http://star-k.org/kashrus/kk-vegetables-wax.htm And I want to the thank the Canadian mom who suggested I might have an Oral Allergy Syndrome. Forgive me for being graphic here, but it never occurred to me that hay fever could cause me to vomit after eating an apple. It occurs to me I should take this much more seriously than I have been. I don't totally understand what Oral Allergy Syndrome is yet, and am not clear if the itchy rashes are part of it (from things like latex, and chestnuts, and soy products and casein). I'm sure the vomitting associated with casein and clams are separate issues. 
Thanks Again, Selena