Reddened skin is often only seen in horses (Paints, Appaloosas, and Pintos) with white haired or pink skinned areas, and especially in anatomic areas where the hair is absent or short, like the muzzle, face, around the eyes, around the anus and vulva, on the sheath or on white limbs.

Skin tumors, infections, allergic skin disease, insects, skin burns and countless other disorders may all result in reddened skin. A hallmark of the healing process is inflammation, the opening of the blood vessels. This allows infection fighting and healing elements from the blood into an affected area. This causes skin to appear red. The other hallmarks of healing are swelling and local pain. Reddened skin in an area is also commonly caused by sunburn.

Male horses with pink sheath skin often produce reddish colored smegma, which can make the sheath or penis area look inflamed when it isn't.