OT - for the 7 year old, I recommend first, before you start the diet, do a stool antibody test from enterolab dot come (you can order it yourself) for both gluten and dairy. Easier that sticking a kid for a blood test, and it's pretty sensitive.
Then you might start with just a month of a dairy-free gluten-free egg-free diet (those are the most common 3 I see on tests, and often found together). If that seems to help things, and nothing shows on the stool test, you might try reintroducing one at a time to see if you can find the culprit.
If that doesn't answer the question, then you can do a full-on elimination diet, starting with 3 days of just lamb, pears and rice, and then adding in one new food every day. If a food seems to cause a reaction, remove it again for a few days and try reintroducing.
Life Extension does offer a food allergy blood test you can order yourself somewhat similar to the U.S. Biotek one that I use, (although not as reliable). I like to say this test doesn't CONVICT any one food, but it does give you a police lineup of the likely culprits. I'd do the stool test on the 7 year old and consider the Life Extension test for hubby.
