If this horse is a gelding, I'd ask them if they
ever noticed it also getting summer sores around the sheath. Last summer a
friend had one break out with summer sores around the mouth, and the sheath. We
worked hard to keep the flies off the sores, using a lot of Swat. I think it is
a larvae / parasitic issue, and maybe one of the vets can chime in. Thankfully,
I've not had it on any of ours. it was indeed a pain to treat. Good luck Melody.
Those kids of yours are getting big enough to go do some rides pretty
soon!