So what actually is mud-fever we hear you ask? ‘Mud-fever’ as we will call it, goes by many different terms such as; rain scald (or rain rot), equine dermatitis, scratches or greasy heel. It is a collective term for what is essentially a bacterial, and in some cases fungal, infection that causes irritation and inflammation of the skin. It will often present itself in moist conditions and mostly affects the heels of a horse – however it can present itself anywhere on the body and will commonly also affect the face, shoulder, back and rump of a horse, where it may be referred to as rain scald.