The Amazing Health Benefits of a Hot Bath
- Nature Source Chaude
- Published on
- Updated on 24 April 2025
Throughout history, the use of baths has been established in many different countries. However, depending on the era, people have considered them either useless or indispensable. It’s only recently that research has recognised their many health benefits. However, the effects of water on the body remain complex and vary according to its form, temperature, duration of use and the environment in which it is found. In this article we will see that the medical qualities of hot baths are undeniable and can help the body to recover.
IN SUMMARY :
What is a hot bath ?
Bathing generally refers to the immersion of part or all of the body in an environment other than its natural environment, for more or less prolonged periods of time. Baths can therefore take many forms (gaseous, liquid, solid, etc.).
In a hot or warm water bath, the body is surrounded by a liquid in which it must remain for several minutes, sometimes up to an hour or more. The body is thus affected by three physical effects: heat, water pressure and buoyancy. An effective bath involves taking advantage of these three physical effects.
Bathing at home allows people to come into contact with this liquid element and enjoy its physical effects. As we shall see, some of its benefits can even be superior to physical exercise. However, you can also enjoy a better quality hot bath in hot springs.
1. Improve blood circulation
The combined action of water pressure and heat naturally promotes good blood and lymph circulation. This improved circulation helps the body to better oxygenate its cells, remove waste and pain more efficiently and better nourish its tissues better, promoting better overall health.
💡In a hot spring, water is often accompanied by gaseous compounds such as hydrogen sulphide (H₂S) and carbon dioxide (CO₂). Carbogaseous water (CO₂) considerably increases blood flux and micro-circulation (in the smallest vessels) in the skin as measured by laser-Doppler. It leads to a significant increase in tissue oxygenation.
2. Influences breathing and soothes the airways
When you soak in a hot bath, the enormous pressure exerted by the water, as we saw earlier, will increase the rate of breathing. As for the heat, it acts not only on the speed of respiratory movements, but also on their amplitude and depth.
A warm bath up to the neck puts the body in a good breathing position and improves oxygenation. This condition also facilitates the inhalation of warm water vapour, which helps to clear congested secretions and excess mucus from the airways. A hot bath can relieve cold and cough symptoms.
💡When soaking in a hot spring water, the thermal vapours and gases inhaled have powerful therapeutic properties on the respiratory tract. To find out more, I invite you to read the end of the article: How to Cleanse your Lungs with Simple, Natural Ways ?.
3. Improves glucose metabolism and reduces inflammation
Research suggests that immersing the body in a hot bath may have a beneficial effect on metabolic diseases such as diabetes. The hot bath may improve insulin sensitivity and reduce inflammation through a variety of mechanisms that are still poorly understood.
Passive heating of the body in a hot bath leads to the release of proteins that help to lower blood glucose levels.
One of these is HSP70, a heat shock protein that is present in the body under normal conditions. It is also produced when the body is exposed to stress such as heat, radiation, infection or inflammation. When induced by a hot bath which has a high thermal effect, this protein triggers various mechanisms that have positive consequences for metabolic health and certain aspects of the inflammatory profile.
In a British study[1], the calorie consumption of 14 men was measured after one hour in a hot bath at 40°C or after one hour of cycling. A meal was also taken immediately after these two conditions to measure changes in blood glucose levels.
→ The results showed that cycling burned more calories (slightly more), but peak blood glucose levels were 10% lower after the hot bath. According to these results, cycling caused a twofold increase in interleukin (IL-6), a biomarker of inflammation, and a similar increase in HSP70 protein production compared to the bath. This increase in inflammation during exercise or a hot bath is normal :it results in an increase in HSP70 and interleukin-6, which promote an anti-inflammatory environment. So a hot bath without exercise is a winner in terms of blood glucose, but not in terms of calories.
Data has also shown that people with diabetes who take frequent hot baths have better HbA1c levels, an indicator of blood sugar control.
💡HSP70 was shown to increase even more when bathing in a hot spring than in a conventional bathtub.
4. Improves cardiovascular health
During a bath, the effect of the heat and pressure of the water on the body causes an influx of blood from the peripheral blood vessels to the heart, improving cardiac function.
In a Japanese study conducted over 20 years (1990 to 2009), 30,000 participants were monitored and classified according to how often they took hot baths each week.
The results of this study[2] were published in the journal Heart in 2020. They showed that those who bathed daily had a 28% lower risk of developing cardiovascular disease and a 26% lower risk of stroke than those who bathed less than twice a week.
→ These results are thought to be due to the heat, which causes an increase in body temperature, heart rate and contractility, blood flow and a decrease in total peripheral vascular resistance.
In a study[3] published in 2021 in the Journal of Applied Physiology, In a study[3] published in 2021 in the Journal of Applied Physiology, 12 participants were exposed to moderate exercise for 60 minutes or to a hot bath at 41°C for 60 minutes. In the 2 conditions, measurements were taken before, during, and 60 minutes after including heart rate, blood pressure as
well as several other parameters.
→ The results showed that immersion in a hot bath led to similar or even greater vascular changes than moderate exercise, and with a lower cardiac load (stress).
A hot bath can also prevent the formation of blood clots. The heat of the water in a bath affects the inner walls of the blood vessels, which then secrete a proteolytic enzyme, t-PA, which is able to dissolve blood clots. This effect can last for up to 6 hours after the bath. Similarly, blood pressure remains lower for several hours after a hot bath.
5. Relieves tired muscles and reduces pain
Contact with heat increases the contractibility of the muscular system and reduces pain. The activation of the blood circulation immediately relieves sore muscles, joints and lower back pain. The changes in muscular blood flow stimulate complex mechanisms that lead to tissue repair.
According to a study[4] published in Exercises and Sport Sciences Reviews in 2021, the application of local heat (targeted therapy) accelerates muscle recovery by reducing muscle soreness, increasing muscle replenishment, stimulating muscle protein synthesis and correcting exercise-induced vascular and mitochondrial dysfunction.
Finally, heat can raise the pain threshold of the smallest nerve fibres (known as type C). These C-fibres are sensitive to thermal, mechanical and chemical stimuli.
6. Provides deep relaxation
The reason people feel so good in a hot bath is because of the relaxing effect. What’s more, this effect lasts for several hours after the bath.
In water, buoyancy makes the body lighter. Your weight is reduced by 1/9 compared to your weight outside, which allows you to relax both physically and mentally. The muscles that support each part of the body relax and tension disappears.
When body temperature rises and the body is relaxed, the brain more easily converts brain waves into alpha waves. When these alpha waves are produced, the brain releases a hormone called beta-endorphin. This hormone plays an important role in immunity and stress reduction.
What temperature to choose?
→ If the temperature of the bath is warm (35-38°C) and close to the temperature of the skin, the caloric element calms all parts of the nervous system. At these temperatures, the parasympathetic nervous system becomes dominant and the bath can be taken for a longer period (> 1 hour). As a result, you will feel more comfortable, calmer and less anxious.
→ If the temperature of the bath is high (42-44°C), the heating element will stimulate all parts of the nervous system. The sympathetic nervous system is more active. The bath should then be shorter (less than 5 minutes).
💡Chromogranin A (CGA) is a protein involved in the body’s response to stress. According to saliva tests, its concentration decreases when the body relaxes in a hot bath and decreases even more in a hot spring. A hot bath in a peaceful, natural environment provides a particularly deep relaxation for the body.
7. Fights depression
A hot bath can also help to fight depression.
In a study[5] published in 2020 in the journal BMC Psychiatry, 45 patients suffering from moderate depression were monitored while they underwent either 15-20 minute hyperthermal baths (temperature of 40°C) twice a week or a moderate intensity exercise programme (walking, running and stretching) for 45-50 minutes.
→ Several tests were carried out and the results, based on the Hamilton Scale (an assessment test that measures depression), showed a greater reduction in depressive symptoms in the “hyperthermal bath” group. The heat of the water, which raises the body temperature, may therefore cause changes in the brain by increasing the production of serotonin, a hormone that is particularly involved in mood regulation.
In the 2019 International Journal of Environmental Research and Public Health[6], we can read: “Immersion in warm water was beneficial for maintaining brain function and homeostasis by increasing the concentration of brain-derived neurotrophic factor (BDNF), a neuronal inducing factor, and decreasing the concentration of cortisol, commonly known as the stress hormone. BDNF is a protein (neurotrophin) that plays a key role in the mechanisms of depressive episodes (DE).
💡Natural light also stimulates the production of serotonin in the brain. An escape into nature or taking an outdoor thermal bath allow you to enjoy the sun’s rays for hours on end.
8. Improves sleep
During the fall asleep phase, your body temperature needs to drop by 1 to 1.5°C for you to fall asleep. Good quality sleep is closely linked to efficient heat dissipation.
When body temperature rises during a hot bath, it means that the body needs to cool down to return to normal body temperature. As a result, peripheral blood vessels dilate to dissipate heat more efficiently.
For people who need to calm down or relax before going to bed, it is recommended to take a hot bath (38-40 degrees) at least one to two hours before going to bed.
A meta-analysis[7] published in 2019 in the journal Sleep Medicine Reviews showed that passive water-based heating, such as a shower or bath, taken 1 to 2 hours before bedtime for at least 10 minutes improved sleep.
A hot bath is therefore a simple way to improve the quality of your night’s sleep and reduce excessive daytime sleepiness, particularly by promoting better body heat dissipation.
However, it is important to take into account daily and seasonal biological rhythms in order to achieve deeply restorative sleep.
9. Strengthens immunity
Normal body temperature is between 35.7°C and 37.3°C, depending on the individual. In fact, the body does everything it can to keep this temperature constant. When exposed to stimuli (or stress) such as passive heating, the body develops functions to protect itself. One of these is to strengthen biological defences and immunity.
Immune cells are more active when the body temperature is higher. It is said that if your body temperature increases by 1℃ above normal, your immunity increases by up to 5-6 times, and conversely, if your normal body temperature decreases by 1℃, your immunity decreases by 30%.
Among the many immune cells are natural killer (NK) cells. When they detect cancer cells or cells infected by a virus, they launch an attack. After a hot bath, the activity of NK cells increases for 1 to 2 days.
10. Supports healthy skin
When applied to the skin, heat increases its temperature and improves blood circulation. A bath improves circulation in all areas that receive heat. The hot water opens the pores, promotes better oxygenation and better elimination of waste and impurities from the skin.
However, a hot bath at home can sometimes have disadvantages, such as drying out the skin.
This can happen for a number of reasons.
Water quality may be too hard and a filter may need to be installed. Soaps and shower gels with a strong detergent action can easily damage the skin barrier and upset the balance of the skin’s microbiota. What’s more, the water in a tub is not renewed as it is in a natural hot spring.
If you have sensitive or dry skin, you should limit your bath to 15 minutes.
💡In a thermal bath,skin hydration improves. It differs from domestic baths in that it contains bioavailable mineral salts (⚠️ when the thermal water is renewed at will) and numerous chemical substances produced by micro-organisms, all of which are useful for skin regeneration. In a natural hot spring, the water is constantly renewed, ensuring a constant temperature in the pool.
In Conclusion
A domestic hot water bath can be a useful addition when the body is tired and needs to rest. Nothing is more restorative for an exhausted body than contact with warm or hot water. However, it should not replace physical activity, which remains an important part of a healthy lifestyle.
A hot bath in a tub enables the body to be mainly affected by these 3 physical elements of heat, pressure and buoyancy , but it can also have a few disadvantages. The confined space of a bath and the increasingly low water temperature can make you feel uncomfortable. A hot bath uses a lot of water or more energy if the water temperature is regulated.
The recommended bathing times are to raise the body temperature by 1°C (hyperthermic bath) :
- 20-30 minutes for a bath at 39°C,
- 15 minutes at 40°C,
- 10 minutes at 41°C,
- 5 minutes at 42°C.
These bathing times are valid for domestic baths and baths in a hot spring.
💡In a hot spring bath, when the temperature is between 27 and 38 degrees, the body can spend more time in the water. In addition, the longer the body is in contact with the thermal water, the more chemical elements are absorbed by the skin. The body also benefits from the powerful effects of grounding.
References
[1] Faulkner, S. H., Jackson, S., Fatania, G. and Leicht, C. A. (2017) Temperature, 4(3), pp. 292–304.
[2] Ukai, T., Iso, H., Yamagishi, K., Saito, I., Kokubo, Y., Yatsuya, H., Muraki, I., Eshak, E. S., Sawada, N. and Tsugane, S. (2020) Habitual tub bathing and risks of incident coronary heart disease and stroke, Heart. BMJ Publishing Group Ltd and British Cardiovascular Society.
[3] Francisco, M. A., Colbert, C., Larson, E. A., Sieck, D. C., Halliwill, J. R. and Minson, C. T. (2021) Journal of Applied Physiology, 130(5), pp. 1362–1372.
[4] Kim K, Monroe JC, Gavin TP, Roseguini BT. Local Heat Therapy to Accelerate Recovery After Exercise-Induced Muscle Damage. Exerc Sport Sci Rev. 2020 Oct;48(4):163-169
[5] Naumann, J., Kruza, I., Denkel, L., Kienle, G. and Huber, R. (2020) BMC Psychiatry, 20(1).
[6] An, J., Lee, I. and Yi, Y. (2019) The Thermal Effects of Water Immersion on Health Outcomes: An Integrative Review, MDPI.
[7] “Before-Bedtime Passive Body Heating by Warm Shower or Bath to Improve Sleep: A Systematic Review and Meta-Analysis.” Sleep Medicine Reviews. W.B. Saunders. April 19.
