At one time or another, many horse owners have experienced the frustration of trying to clear up that red, scabby, oozing, irritated skin inflammation on the back of their horses' pasterns. Known by a variety of names such as dew poisoning, mud fever, and scratches, the condition is common when horses spend time walking through damp pasture grass, but it can also be found in arid climates where the horses are kept in drylots. Sometimes the condition is fairly mild and does't seem to bother the horse, but a bad case can cause bleeding, pain, and lameness. Repeated irritation leads to scaling, scarring, and thickened skin.