My stallion use to do this, I used eye wash in them everyday once a day and they were a lot less teary. You do not have to buy those expensive clear eyes horse eye wash but you can buy eye wash from wal mart and it works great. It is most likely just dust allergy.
You know how to make a miniature horse even smaller? Leave them in the dryer a little longer!
"Don't ever regret something that once made you smile"