The sheath is a large fold of skin that encases and protects the horse’s penis. It is composed of skin and many glands that secrete a waxy substance called smegma. These secretory glands are also concentrated in a pouch that lies next to the urinary opening of the penis.
The inner sheath is a warm, moist environment of folded skin. Any irritating substances left in this area will cause inflammation and swelling that can be seen externally. Excessive smegma accumulation around the urinary opening of the penis is often called the “bean.” A large accumulation in this area can also cause swelling, as well as painful urination. Contrary to popular belief, however, smegma accumulation will not block the ability of a horse to urinate.
These conditions are not life-threatening, but a swollen sheath needs to be cleaned. This is best accomplished under sedation by a veterinarian. Sedation calms the horse, allows the penis to drop, and facilitates visual inspection of the area. Careful inspection is important, since, rarely, the swelling is caused by a tumor that must be treated in a timely manner.
Many owners choose to clean their horse’s sheath themselves. No harm can come from this practice as long as all irritating substances are rinsed from the area after it is cleaned. Mild soap can be used, as well as any dish soap. All soaps are irritating and must be rinsed thoroughly. The best tools for the job are the hose or water from a 60cc syringe. An easier alternative to soaps is to apply a generous amount of KY jelly to the sheath and penis and let it sit for 20 minutes. Wipe the area well with paper towels – there is no need to rinse. KY is nonirritating and dissolves smegma extremely well. It has become my treatment of choice for cleaning sheaths – especially for horses that seem to swell up frequently. Many of these horses appear to be sensitive to soaps and detergents, even if they are rinsed well.
A final note – take all necessary safety precautions when cleaning a sheath. Many horses strongly object to the procedure.