Raustyk has had extensive allergy testing in the past. It's very similar to human allergy testing, onsiously the more extensive the test the more envolved it is. This should be done by a specialist only. They shave a patch of hair & inject a bunch of different common allergy causing substance, wait 24-48 hours (can't remember for sure). They then examine the area to see what locations are irritated.

Does she happen to eat out of plastic bowls? That could be part of the problem thats causing the irritation around the mouth. It's very comon for dogs who eat out of plastic to get allergy/pimple type symptoms on the muzzle.