Well Horse; it might be a little expensive but it works in about a week. When I first got my mare she had the worst case of scratches I've ever seen. Her ankles were swollen, and her hind legs was very sensitive. After a week of stall rest and spraying the Well Horse on every night it was pretty much gone, besides a little area. Make sure you brush off the mud (wet or dry) when you bring them in to help prevent it, and if you can wash the area with ivory soap once a week to help prevent scratches.
Also its always good to have on hand. The mare I talked about above also had a case of rain rot or dry skin (looked like rain rot but didn't want to use Mycro Tech because if it wasn't it would burn and cause more damage then good) so I sprayed her with the Well Horse and it cleared up in a few days.
This is what it say on the box:
Antibacterial Resin & Enhanced Healing
Open Wounds, Scratches, Rain Rot, Ring Worm, Skin Fungus, Dew Poisoning, Cracker Heels, Hot Spots
100% Rain Forest Natural & Organic Remedies
Can be used on ALL animals.
Here are some images of what the well horse did for open wounds, so imagine what it'll do for your scratches!