Jenny,
I just wanted to answer your question about the tests they do. Claire (18 mo) had allergy testing done about 3 months ago. The test is not fun, if possible I would take dh or someone with you. I went alone and wish I hadn't.
They will talk to you about the possible allergies and ask a ton of questions. The test itself is adminstered on the back, sometimes the arm. They will prick two places first, one with a saline solution and one with a histamine. These two pricks are the test pricks which they use to compare the other pricks to. They will then prick for each allergen they wish to test. If they only test peanuts, or the legume family, it may not be many, however, the allergist may want to also test the tree nut family or anything else based on your conversation. Claire had 25 pricks. They write on the back to show what is what and then they start pricking. OUCH. When done they wait 10-15 min and then "read" the results. The pricks are with a little needle like that which people prick their finger for blood sugar testing.
Anyway, I hope that answers your questions. Maybe take a special treat for dd to eat after the pricks while you wait. Here's hoping for no allergies and like the rest of the ladies said, I would stay away from the PB until then.
Myia