That sound like fungus for me. You can use GSE(Grapefruit seed Extract) and this kill any fungus, bacterial infections, etc. I use this for my animals, family and me. I noted a red-pink mark in my right hand, this mark started to grow and itch. Well, i though this must be some kind of fungus, so i began to put GSE, one drop in this mark everyday, that was a week ago. This mark disappears, my skin heals very well.
There is an excellent site about natural healing therapy for animals, with lot of information, if you want to see it, www.shirleys-wellness-cafe.com. I use natural therapy for my animals with excellent results.