Warm-Water Bathing, Aquatic Exercise, Aquatic Physical Therapy, Spas and Sitz Baths

How to Use This Guide

Warm-water practices are the most familiar part of hydrotherapy, which means using water for comfort, exercise or rehabilitation (see what hydrotherapy is). This page gives a short summary of each practice and points to a page with the detail. It is information only and gives no temperature, time or schedule to follow. Water trials cannot be blinded, and many outcomes are self-reported comfort. Hydrotherapy is at most an extra and does not replace care for a health problem.

At a Glance

Warm Baths and Showers

A warm bath or shower is the simplest form of hydrotherapy. The best-studied question is sleep. A 2019 systematic review of 17 studies found a warm shower or bath before bedtime was associated with better self-rated sleep quality and sleep efficiency, and that timing it 1 to 2 hours before bed was linked to falling asleep sooner. The authors said research was scarce and the best timing and duration were still unclear. [1] Label: promising but limited.

The NHS lists a bath as one way to relax before bed for insomnia. [12] For more, see warm baths and sleep and relaxation for sleep.

Hot water can scald: the NHS notes that scalds are caused by hot liquids or steam, [13] and Parachute Canada says a child's skin burns more quickly. [14]

Epsom Salt Baths

Epsom salt is magnesium sulfate. [15] The popular idea is that soaking lets magnesium pass through the skin into the body. A 2017 review concluded that the propagation of transdermal magnesium is scientifically unsupported, and noted that a bath study it described had been published only on a commercial website, not in a peer-reviewed journal. [2] That is a statement about the absorption claim, not about the comfort of a warm bath. See Epsom salt baths: claims and evidence and the ingredient page on Epsom salt.

Hot Tubs and Whirlpools

A hot tub is a tub of heated, filtered water, often with jets, that can be shared. HealthLink BC, a British Columbia public-health service, says hot tubs and pools can provide an environment for bacteria to grow, including Legionella and Pseudomonas. [3] The NHS lists spa pools and hot tubs among sources of Legionnaires' disease, a lung infection. [16] A US review of 493 outbreaks tied to treated recreational water, including pools and hot tubs, found Legionella caused 16% and Pseudomonas 13% of outbreaks with a confirmed cause. [17]

Hot tub use in early pregnancy was linked to about twice the risk of miscarriage in one cohort study. [18] See hot tubs and whirlpools and hot tubs in pregnancy.

Sitz Baths

A sitz bath means sitting in shallow warm water so the hips and bottom are covered. The NHS suggests a warm, shallow bath after a bowel movement to ease the pain of an anal fissure, [19] and a warm bath to ease itching and pain from piles. [20] A systematic review of four trials found no significant effect on pain or healing, although patients were satisfied with the sitz bath. [4] Label: mixed. See sitz baths.

Hot and Cold Compresses and Packs

For back pain, the NHS suggests an ice pack or a heat pack, each wrapped in a tea towel. [21] A Cochrane review found moderate evidence from a small number of trials that heat wraps give a small short-term reduction in low back pain, and insufficient evidence to judge cold. [5] See hot and cold packs.

Steam Inhalation

Breathing steam is a long-standing home remedy for colds. A Cochrane review of six trials said it was uncertain whether heated, humidified air relieves cold symptoms. [6] Dutch burn-centre data showed most steam-inhalation burn victims were children. [7] The NHS says not to let children breathe steam from a bowl of hot water because of the risk of scalding. [22] See steam inhalation and steam towels.

Aquatic Exercise

Aquatic exercise means exercise in a pool, such as water walking or water aerobics. The NHS lists swimming and aqua aerobics among low-impact activities for people with rheumatoid arthritis and suggests asking a physiotherapist for guidance. [23]

For knee or hip osteoarthritis, a Cochrane review of 13 trials (1,190 participants) found aquatic exercise gave small, short-term improvements in pain, disability and quality of life compared with no intervention. [8] Label: established, modest effect. In fibromyalgia, one meta-analysis of 7 trials found aquatic therapy improved sleep quality but urged caution because there were few studies, [24] while a larger one found only a trend that was not statistically significant for sleep, with very mixed results between trials. [25] Label: mixed. See water exercise classes and aquatic therapy for osteoarthritis.

In pregnancy, the NHS says swimming can be good exercise because water relieves pressure on muscles and joints, and advises telling the instructor, keeping cool and stopping if you feel too hot or unwell. [26]

Aquatic Physical Therapy

Aquatic physical therapy is exercise in water prescribed and supervised by a licensed clinician, usually a physical therapist, for a specific problem. It differs from a general water class because the clinician sets goals and adjusts the program. A 2026 meta-analysis of trials after knee replacement found hydrotherapy did not reduce pain more than land-based exercise or usual care, but gave moderate gains in lower-limb strength; the authors said program differences and few high-quality trials prevent firm conclusions. [9] Label: mixed. Rules differ by country and US state, so check a therapist's license with your local licensing board. See aquatic physical therapy.

Spas and Mineral-Water Bathing

Balneotherapy (spa therapy) means bathing in mineral or thermal waters. An umbrella review of 49 reviews concluded spa therapy appeared beneficial for some musculoskeletal conditions, with improvements potentially lasting up to 9 months, but noted limitations in the evidence. [10] A 2025 review of 42 trials in rheumatology rated the certainty of the effect as very low, [11] while a 2024 meta-analysis of 16 fibromyalgia trials found large pain reductions maintained up to 6 months. [27] A Cochrane review of mineral baths for osteoarthritis found "silver level" evidence of benefit, but adverse events were not measured. [28] Label: promising but limited. See balneotherapy.

Who Should Take Extra Care

People with heart disease, high or low blood pressure, diabetes with reduced skin sensation, or who are pregnant or take blood pressure medicines should ask a clinician first. A 2026 review found heat therapy consistently caused short-term drops in blood pressure, and that safety margins in frail older adults and beta-blocker users are not well defined. [29] Being too hot is a listed cause of fainting. [30] If someone faints, has chest pain or is not breathing, call 911 in the US. More is on the hydrotherapy safety page.