Bald under his armpit???

[moodymare1987]

Ben has rubbed away the fur under his armpit. It is only on one side, Its not girth gall or anything, you have to look right under his chest to see it. What could it be? He had something like this last year, I assumed it was grease rubbing or somthing. Anyone have any ideas?
I will try get pics to show you what It looks like later.

 

[TGM]

Some types of sarcoid appear like this and the armpit is a common place. My old mare had one, which disappeared without treatment.

 

[BeckyD]

I had the same thing where Ronnie's martingale loop that the girth goes through had got caught and had rubbed his armpit during a ride (bless him, he hadn't complained tho it must have been very sore - hairless and weepy!!). Could it be something similar?

 

[moodymare1987]

Oh ok it goes after a bit though, he gets a bit sweaty under his armpit and I guessed it was just down to that.