can someone tell me what this is?

Did he have an injury of some sort that you didn't notice? It could be proud flesh. The other thing is maybe a parasite (doubtful)??? It looks more like an injury with proud flesh. There are only 2 other things that come to mind; viral warts and (not to scare you, so don't take my word for it) a sarcoma. I would suggest if it doesn't get better or seems worse in the next few days (a week) to call a vet and have it looked at. I'm still leaning towards an injury that healed wrong. I stand corrected, sarcoid, not sarcoma... LOL

ADD: The sarcoids are commonly caused by biting flies that have bit other horses that already have the sarcoids, and usually only if the horse is susceptible. It looks very much like a Fibroblastic Sarcoid. Call your vet to get whatever it is identified.

It's definitely not ringworm.

I would get the vet out to be certain but it looks like a sarcoid.

It doesn't look too uncomfortable where it is so it shouldn't bother him too much but all the smae I would get him checked.

It looks like a sarcoid to me. Don't mess with it, or it may spread or enlarge. You should have your vet evaluate it and don't do anything that isn't advised by the vet.

i bought a horse that had had skin cancer. the vet said it wasn't fatal. previous owners had cut them off (themselves. how stupid can you get??) and she had a few flat scars from that.

my riding teacher saw the spots (she still had one on her neck that looked just like the spot your horse has) and said that there is an ointment that you can put on those and they just die and fall off. might be good to try!

Looks like a boil.

I think it looks like a sarcoid

http://en.wikipedia.org/wiki/Equine_sarcoid

http://www.google.com.au/images?hl=en&q=sarcoids%2...

No its definately not a ring worm here's some google pics of them http://www.google.com.au/images?hl=en&source=imghp...