Peanut allergy?

So yesterday while my DD (6 months old) was napping at her daycare providers, my sitter had toast with peanut butter.  After DD woke up her sitter gave her smooches on the neck like she always does.  About an hour later her cheek was bright red and warm.  She though it may be a reaction from her 6 month shots the day before, but her temp, etc was normal.  She then thought of her kissing her and a reaction.  It was a peanut butter powder that you mix with water to make...less fat or something.  When I picked her up I took a small amount and put it on her leg (stupid I know, but she's right next to the hospital, God forbid anythin ghappend).  We wait a bit and she was fine. we got home and she woke up from her nap and her leg was fine, but the saw that her arms had hives all over them.  I called the dr. and took her in.  She ordered blood work and referred to allergist to see and gave epi pen in case.  I took her for bloodwork today and awaiting results in a few days.  MY question is, has anyone ever experienced this and found out it was an allergy and was it serious or mild?  Or anyone find out it was nothing?  Just curious.  We have always eaten peanut butter and all kind of nuts regularly in our house and were never careful and no reactions at all until yesterday....I know it can increase.  Just trying to hear similar stories.
Thanks