Also check up inside her thighs, between her teats, in the drk corners of the anal area, tip of tail, in the forelock and in the ears if she starts shaking her head.
I feed three of my horses processed garlic; the fourth can't have garlic because he has ulcer issues.
They still do get a few ticks. I keep the areas washed twice daily. I then make a mix of hemerhoid ointment, antibiotic ointment, and diaper rash cream. The diaper rash cream holds everything on a lot longer so the flies stay off the open sores.
Some horses will welt up really bad over a tick bite, others hardly at all. It can take the sores a week to a month to heal, depending how bad of a reaction the horse had.
Some folks swear by Endure fly spray. I have heard other folks say to put powdered sulphur in a sock and whap the sock against the horse's legs. If your horse is in tall grass that might not work.
MTG works because of the sulphur but it is waaaaay too hot to put MTG on a horse - it will burn and blister them; I've already read about that on another forum.
Hope this helps:)