There are lots of different items you can buy at your local tack store geared towards healing a cut on your horse. A few of them have ingredients that can be hard to read. However there are several more natural methods that have been used for years that cure equine cuts just as well. Maybe even reduce scarring.
One method is honey. Try picking up the most natural and organic product you can find. This will work the best. Also try hydrogen peroxide or witch hazel. Both can be found at any drug store and are fairly inexpensive. Witch hazel is also reputable for reducing scarring.
In another event that your horse has a healing cut that has already scabbed, apply vitamin E oil to reduce scarring.
Hydrogen Peroxide Bonus: it can also be used to keep your greys and the whites on your horses white. Apply some to a dirty area and send them out in the sun where it will whiten.