Balneotherapy is the therapeutic practice of bathing in naturally occurring mineral water from thermal springs. Unlike a regular hot bath or a soak in a swimming pool, balneotherapy relies on water with specific mineral content (at least 1 gram per liter) and warm temperatures, typically between 36°C and 42°C (97°F to 108°F). It has a long history in European and Japanese medical traditions and is still prescribed today for conditions ranging from chronic joint pain to psoriasis.
How Balneotherapy Works
The therapeutic effects come from two sources working together: heat and mineral chemistry. Warm water dilates blood vessels, eases muscle tension, and triggers the release of the body’s natural painkillers, including endorphins. The buoyancy of the water also takes pressure off joints, which is why people with arthritis or back pain often feel immediate relief during immersion.
What sets balneotherapy apart from ordinary warm baths is the mineral composition of the water. Thermal spring water contains dissolved minerals like sulfur, magnesium, selenium, silicon, and bicarbonates in concentrations high enough to interact with the body. Sulfur-rich waters, for instance, have anti-inflammatory and immune-regulating properties that benefit skin conditions like psoriasis and eczema. Different springs have different mineral profiles, and the type of water used often determines what condition is being targeted.
Mineral waters are classified by their dominant chemical components: sulfurous, chlorinated, sulfated, bicarbonated, ferruginous (iron-rich), and carbogaseous (carbon dioxide-rich). Each type has a somewhat different therapeutic profile, though there is overlap. Sulfurous waters are the most widely studied, with documented benefits for skin disorders, respiratory conditions, and chronic inflammatory diseases.
How It Differs From Hydrotherapy
The terms “balneotherapy” and “hydrotherapy” are sometimes used interchangeably, but they refer to different approaches. Hydrotherapy uses ordinary water in various forms, including ice, steam, and liquid, with temperature as its primary therapeutic tool. Balneotherapy specifically requires natural mineral water from recognized thermal springs, and its effects depend on both the physical properties (warmth, pressure, buoyancy) and the chemical properties of that water. Aqua therapy, a third category, focuses on exercise performed in water to rehabilitate musculoskeletal or neurological problems. In practice, these categories often blur, especially at spa facilities that combine multiple approaches.
Conditions Treated With Balneotherapy
The conditions most commonly treated with balneotherapy fall into three broad categories: musculoskeletal, dermatological, and metabolic. The strongest body of evidence supports its use for osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, low back pain, psoriasis, and atopic dermatitis (eczema). Fibromyalgia is another frequent indication, though results vary more between individuals.
Sulfurous mineral waters have also been used as inhalation therapy for respiratory conditions. Breathing in sulfurous water vapor has shown benefits for people with chronic obstructive pulmonary disease (COPD) and other airway disorders, performing better in some comparisons than standard saline inhalation.
What a Typical Treatment Looks Like
A standard balneotherapy session lasts about 20 minutes, though some protocols extend to 30 minutes or longer. Sessions are usually scheduled once per day, though some treatment plans call for twice-daily sessions or as few as one to three sessions per week. The overall course of treatment varies widely. Short programs run about 10 days, while longer programs can stretch to 24 weeks. Most fall somewhere in the range of 10 to 15 sessions.
During a session, you simply soak in a bath or pool filled with thermal mineral water. Some programs add mud packs (pelotherapy), which use mineral-rich mud applied to the skin before or after bathing. A meta-analysis published in BMJ Open found that the combination of baths plus mud packs produced the largest pain reductions in people with rheumatic conditions.
Evidence for Pain Relief
The most robust research on balneotherapy focuses on pain in rheumatic conditions. A large systematic review and meta-analysis covering thousands of patients found moderate pain reduction at the 3-month mark, with the effect still detectable at 6 months. By 12 months, the benefit had largely faded, suggesting that balneotherapy works best as a periodic or repeated treatment rather than a one-time intervention.
The size of the benefit depends on the condition. People with mechanical disorders like osteoarthritis and low back pain showed the most consistent improvement. Inflammatory conditions like rheumatoid arthritis showed smaller, less certain benefits. Fibromyalgia results were highly variable, with some individuals reporting major relief and others showing little change. It is worth noting that the overall quality of evidence in balneotherapy research is considered low, largely because it is difficult to design a convincing placebo for a mineral bath. Study participants generally know whether they are soaking in thermal water or tap water, which introduces bias.
Effects on Stress and Sleep
Balneotherapy also appears to meaningfully reduce psychological stress. A randomized controlled trial measuring both self-reported distress and salivary cortisol (a hormone your body produces under stress) found that even a single week of daily sessions reduced stress intensity by 3.5 points on a 10-point scale, a large effect. Two-week programs produced similar reductions. Cortisol levels dropped measurably across all treatment groups, with reductions ranging from 0.67 to 0.87 nmol/L.
Interestingly, winter treatments produced stronger stress relief than summer sessions. A one-week summer program reduced stress by only 1.0 point, compared to 3.5 points in winter. The researchers suggested this may relate to the greater contrast between cold environmental conditions and warm water, as well as higher baseline stress levels during winter months.
Sleep quality also improves with balneotherapy. Multiple studies in people with fibromyalgia, obesity, and musculoskeletal pain have documented better sleep during and after treatment courses. In one study using mineral water with a high concentration of 40 grams per liter, sleep improvements persisted for up to three months after treatment ended.
Safety Considerations
Balneotherapy is generally well tolerated, but the combination of heat and water immersion places real demands on the cardiovascular system. Blood pressure drops during bathing, sometimes substantially. One study found that central systolic blood pressure dropped by about 14 mmHg (a 10% decrease) after two 20-minute soaking cycles in winter. For healthy adults, this is harmless. For people with heart conditions or blood pressure problems, it requires caution.
People with coronary heart disease, serious arrhythmias, or unstable medical conditions are typically excluded from balneotherapy programs. If you take blood pressure medication, maintaining consistent use before sessions is important. In Japan, where hot spring bathing is deeply embedded in the culture, an estimated 19,000 deaths per year are associated with bathing, mostly among elderly people during winter. The primary risk is the sharp temperature change between cold air and hot water, which can trigger dangerous drops in blood pressure or cardiac events.
Practical precautions reduce risk considerably. People with cardiovascular or chronic lung conditions should limit sessions to a single cycle of 20 minutes or less, particularly in summer when cardiac stress from heat is higher. In winter, warming up indoors before entering the bath helps avoid the shock of rapid temperature change. Prolonged soaking in summer is not recommended because of the added strain on the heart from ambient heat combined with hot water.