Originally Posted by Kayty
Looks like Onchocerca to me. I had a pony here get the same bumps this time of year, it was Onchocerca, just wormed her with a paste that controlled that particular worm, and it cleared up within a week.
This...I couldn't think of the exact name but knew it looked similar to what my sister's pony did years ago. We used a paste wormer too and just watched it, keeping it clean..My only other thought would be an allergy to certain fly bites, but if it's only on one side that seems a little odd..