My little sister has always had a pretty severe tree nut allergy. I it was discovered around age 3 when a family friend gave her a bit of pecan pie. She's 26 now and still allergic to tree nuts. She also had childhood allergies to dairy and egg that she outgrew by age 2-3.

She never had allergy testing when she was young. The ped back then didn't recommend it for children. She was clearly very allergic to nuts (which was evidenced every time she accidentally ate something with almond extract or something).

Finally, in middle school she changed Peds and the new doctor said she should have had the skin test a long time before. So she got skin tested and found out she was allergic to shellfish and peanuts as well (although she'd eaten both but never had a reaction).

Recently, she changed insurance and they required an updated allergy test and they did the blood test. This time it said she's not allergic to peanuts OR shellfish, just tree nuts--and she's been avoiding all of them since she was 10 or so.

About 50-60 percent of all blood tests and skin prick tests will yield a “false positive” result, so I guess you really only know by doing a food challenge--which she has done, and feels okay with eating shellfish and peanuts now. But seriously---50-60% of allergy tests yield a false positive? That's pretty high, right? Her new allergist recommended she have a follow up updated skin prick test, which also showed an allergy to peanuts, but she feels fine when she eats them.

If you are a parent or an allergy sufferer yourself, have you dont food challenges with the allergic foods, just to test? Do you periodically re-test to see if the allergy has changed?