u/EveryAd7005

I noticed about a week ago that my Guinea pig had a bald spot behind her ear but wasn’t too worried since it’s pretty Normal for Guinea pigs. Today I noticed it again and that it’s gotten bigger and has some kind of faint brown texture. I plan on taking her to the vet anyways but some kind idea of what this is and if it’s serious can put my mind at ease (it’s wet because I put warm water on it in case it was irritated)