In early fall, when I stayed for her grooming, I noticed my 10 yo rough collie Billie had a patch on her ear (back of the ear, in the middle) that was devoid of hair. She has so much fur I never noticed it until I saw her wet from her bath. It got a little larger but does not seem to bother her in any way. I thought demodex mange but the breeder said it doesn't run in the line, and the vet said that's not what it is anyway. It has, however, spread to her other ear, same place. Does not itch and she seems completely unaware of it. It has not spread to my other three collies. It doesn't have any crustings or anything, just looks pink. The vet's words were "I'm stumped, frankly." A scraping showed nothing, and a blood test showed nothing glaring. Any ideas?