I had what appeared (to me, an allergist, and an ER doc) as an anaphylactic reaction back in Dec. I ended up having about 3 more reactions in the 2 or 3 months following. That led me to an allergist who did skin testing for a zillion things. Environmental stuff, foods, animals, etc. NOTHING reacted. I also have what appears to be pretty bad seasonal allergies but again, reacted to nothing. I did a blood test for celiacs and dairy allergy and both were negative. I know I'm sensative to soy. I've had problems with it in the past and do my best to avoid it. I did not react to soy on the skin test however. I also noticed a few years ago that artificial sweeteners increase my pain levels in my skin tissue (if not cause it). I kicked it out completely but, that makes getting rid of actual sugar even more difficult unfortunately.
Skin testing for IgE allergies doesn't reveal food intolerances. The blood test for celiac for example doesn't reveal non celiac gluten intolerance which has been shown to cause FM and RA symptoms. The ALCAT or IgG testing might be more helpful. Or www.enterolab.com. Or do elimination-provocation testing yourself.
You can also have anaphylactic type responses to food chemicals. Food chemical intolerance does not involve the immune system at all but how the chemicals are broken down or detoxed by the body (or not). For example, salicylates for me were a big trigger of my IC before gut healing and intensive supplements.