4 oz. zinc oxide
2 oz. neosporin
2 oz. miconazole nitrate (desinex or monostat has it)
1 oz. hydrocortizone cream

Trim the hair away from the affected area to expose it to the air. Apply the above to the area once or twice daily. Keep horse out of mud and if they get wet in rain or post-riding rinse, dry their legs thoroughly ASAP. Good luck!