Hydrotherapy is an increasingly popular means of soothing pain, treating various medical conditions and promoting well-being with the use of water. Water in any forms (hot, cold, steam, or ice) can be used in hydrotherapy to promote healing.

The ancient Egyptian, Greek and Roman civilizations were known to use water therapy as a means of improving health. Works on the medical uses of water began to be published in the 18th century, but little scientific evidence to support the alleged benefits became available until recent decades.

Today hydrotherapy is used by millions to ease symptoms of musculoskeletal disorders. The two active agents in hydrotherapy are heat and cold, with the former relieving pain and improving circulation and the later reducing swelling. The therapy has six main forms: packings, hot air baths, general baths, local baths, compresses, and fomentations and poultices.

In hydrotherapy, a pack, or a wet sheet, is commonly used to stimulate or soothe a patient when enveloped around the body. Like packing, hot air baths, also known as saunas, cause the patient to sweat. A hot air bath is typically made up of one or more chambers of varying temperatures in which the patient sits for up to two hours.

General baths can be hot or cold, as can sitz, spinal, foot and head baths, which are collectively known as local baths. When applied correctly local baths can reduce inflammation with alternating between hot and cold bath thought to be beneficial for those with arthritic joints or poor circulation.

Compresses, or bandages, can be used to cool or heat, the former used for fevers and the latter for relief of congestion. Fomentations and poultices can be hot or cold and may use electricity among other mediums.

Hydrotherapy can be practiced at home or at a clinic. Many spas now offer hydrotherapy treatments such as inhalation therapy, when a sauna is scented with essential oils or herbs. Spas are increasingly facilitated with hydrotherapy baths, or Jacuzzis, and Vichy showers that use water jets to massage, relax and stimulate.