Your bath routine could become a medical therapy, according to researchers. A new scientific review shared how your bath could become hot water immersion or passive heat therapy but warned only some people will seeconsistent results.

Published in the Journal of Applied Physiology, the researchers analysed existing scientific evidence around the benefits of hot water immersion. This is a very specific type of bath that works as passive heat therapy by heating the water to certain temperatures.

It’s been used for centuries in Roman thermae, Japanese onsen and Turkish hammams among countless others. It usually requires water temperature to be around 39°C or 40°Cand longer sessions of lying in this water was linked to greater reductions inblood pressure.

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Typical bath water tends to sit between 33°C and 37°C. However it is important to take care as going over 40°C isn’t usually advised as this could lead to overheating.

To practice hot water immersion safely, some strategies include leaving the bath gradually, having a seated recovery period after getting out of the bath before standing, keeping limbs out of the water and to ensure you’re well hydrated before getting.

To use hot water immersion in your everyday life, the researchers suggested having water temperature between 39°C and 40°C and staying in for around 30 minutes or more. Following up this therapeutic treatment with the safety strategies mentioned above.

Immersing yourself in water at these temperatures has immediate effects on blood pressure as your blood vessels dilate and increase blood flow to handle the heat. Early research showed that 15–30 minutes of hot bathing at 40.5°C to 43°C can lower systolic blood pressure to as low as 60mmHg according to News Medical.

The review also found a study linking this type of therapy to reductions in high blood pressure and a 28% lower risk of cardiovascular disease. However, this study was only observational and could not prove that the baths were the direct cause of these benefits.

Older people with high blood pressure that is being treated clinically had more consistent benefits from hot water immersion than young, healthy people and those with untreated hypertension. The latter groups experience minimal effects or no sustained results.

However, blood pressure wasn’t the only thing affected by these baths. Researchers found it also improved sleep quality, reduced stress markers and enhanced long-term psychological health with nervous system changes.

People with diagnosed high blood pressure usually have readings higher than 130/80mmHg. High blood pressure can increase the risk of heart, brain and kidney diseases. But other studies have found that lowering systolic blood pressure by just 10mmHg can cut the risk of a major cardiovascular risk by 20%.

The benefits of hot water immersion are linked to the rise in core temperature which triggers a range of physiological responses that can even mirror exercise. The researchers concluded that hot water immersion “shows promise” as a therapy for hypertension alongside other treatments but warned further research is needed to define protocols and long-term effects were inconsistent.