PiaffNPassage has the right stuff to treat the scratches. I live in SC and our soil is mostly sandy, so I try to use a dry ingredient on my TWH. First, I keep his feathers clipped completely down during rainy season. Then I wash his pasturn with a medicated shampoo – MicroTek is real good or you can use the surgical scrub found in any tack shop or on line at Jeffers, etc. Rinse thoroughly, dry completely and then – I apply a good athlete’s foot powder. This will keep the area dry and not attract sand or dirt. It won’t last in the rain or mud. If the scratches are severe enough, stalling the horse during the rain and or keeping him away from mud will go a long way to help clear up and reduce the incident of the problem.