did you ask the dog owner if the dog eats peanut butter? This may seem like a crazy question but we have SEVERAL frinds and family that actually feed peanut butter to thier dogs!! Different reasons for each one... there is a toy called a "kong" that you put PB in and the dogs play with it and try to get the PB out for hrs., one friend of ours said that their dog had medical problems so couldn't eat (reg. dog food) so the vet. put the dog on PB sandwiches! My brother and his kids just feed PB sand. to their dog because he loves them so much, it is not an uncommon thing for people to feed PB to dogs so if you haven't already maybe you could ask. GOOD LUCK :0)

There are some pet foods that may contain peanuts not only as an ingredient, but as a possible cross-contaminate. There are also dog toys that are injected or permeated with peanuts to encourage the dog to chew them.
So it could be possible for the proteins to have still been in the dog's mouth and on its tongue when it was licking your daughter. I know in humans the protein can remain for up to 8 hours in the mouth.

Hi,
Skin tests from an immunologist were negative for dog hair and dander, however, I am allergic to dog saliva. Even if a dog's wet nose touches my skin, I break out in itchy hives.
My immunologist explained that although dog hair may not effect me, the proteins in a dog's saliva can cause cause an allergic reaction.
Hope this information helps.

Bassball23bb is right about the saliva. Our Allergist told us the same thing about the saliva. Your daughter may be allergic to that as well.

I am not allergic to dog anything but I've reacted to dog saliva before after a dog ate peanut butter based treats.