When your horse suffers a sprain or traumatic injury, or is stall-bound for extended periods, its legs may swell and become warm to the touch. Because inflammation and swelling can damage tissues and cause discomfort, your veterinarian may prescribe a "sweat" bandage as an aid in reducing fluid build-up in the legs.

Although sweat bandages are effective, the science of how and why they work still isn't precisely understood. The purpose of the sweat bandage is to generate heat (which may help dilate vessels and increase blood flow), add pressure and provide support.

Whatever the mechanism, the combined effect seems to help the body dissipate excess fluid from the injury site and reduce inflammation.

While sweat bandages are useful in reducing swelling, they are generally not recommended for recent injuries or those that include open wounds. Be sure to consult with your veterinarian before applying one.

What sets a sweat bandage apart from other wraps is that a "sweating" preparation or poultice is generally applied to the leg, covered with lightweight plastic wrap, and then bandaged.

There are a variety of commercial and homemade preparations that can be used to sweat legs. The formulation your veterinarian recommends will depend on the type of injury and his or her personal preference. Some of these may contain "osmotic" agents that actively help pull fluid from the cells.

Common ingredients used in sweat preparations include:

It is essential to use proper techniqes when applying a sweat bandage. Applied incorrectly, the bandage will not only fail to do its job, it can cause discomfort, restrict blood flow and potentially damage tendons and other tissue. (It is often said that it is better to leave a horse's legs unbandaged than to wrap them incorrectly.)

Remember, padding is essential for protecting limbs. At least an inch or more of soft, cushioning material should be placed between the limb and the support bandage to distribute the pressure evenly and prevent blood flow from being restricted.

If you have never bandaged a horse's legs before, ask your veterinarian or an experienced equine professional to demonstrate the proper techniques. Practice under his or her supervision before doing it on your own.

• Do not leave the sweat bandage on for more than 12 hours. After 12 hours, remove the wrap, allow the leg to "rest" for 12 hours, and reapply the sweat bandage if necessary.
• After unwrapping, take a few minutes to examine the leg. It should be noticeably improved. If there are signs of increased heat, swelling, drainage or skin irritation due to the sweat, consult your veterinarian.
• A horse with a condition requiring a sweat bandage should be confined to a stall or small run unless otherwise directed by your veterinarian.
• If DMSO is an ingredient in the sweating compound, make sure the horse's skin is dry before applying it to reduce the chance of skin irritation. Wear gloves to protect your hands.
• Check the bandage several times a day to make sure it has not tightened, loosened or slipped out of place.
• Make sure the bandage does not cut off circulation, compress tendons, create pressure sores or cause skin irritation, redness or discomfort.
• Monitor and evaluate the horse carefully. If swelling develops above or below the bandage, lameness increases, or the horse becomes distressed or begins to bite, paw or rub the bandaged site, check the leg and contact your veterinarian.
• Watch for any other signs of ill health. If the horse becomes depressed, irritable, loses its appetite or has an elevated temperature, consult your veterinarian.
• If you have any further questions or concerns about sweat bandaging, contact your veterinarian.