I tried several ointments for BigT’s tick bites, and really liked this one by Animal Legends: ADE with Tea Tree oil. It has a petroleum jelly, tacky consistency so with the heat of my hand it smeared up nicely in the pocket between his inner thigh and groin. It softened and conditioned the skin and I saw improvement in the raised bumps left from tick bites within three days.
A couple of things: your horse may be sensitive to Tea Tree Oil (that can irritate some skin types so I would do a test); and it does attract dirt if you used it in an area where the horse is likely to roll (LadyZ got big dirt smears on her butt after I used it on her).
I am thinking it might provide some insect repellant properties too as the tick I removed today from the area was dead. Although, for real bug protection in wound areas opt for Swat.
And, though I had my doubts, Equi-Spot is clearly providing them protection as I’ve found very few ticks on them – but plenty on me! ARGH!