For centuries, people around the world have used water therapy or hydrotherapy. The temperature of the water used can have various health benefits.
Most studies on the health benefits of hot and cold water have used water immersion therapy. In this therapy, a person immerses his or her body, or part of it, in a tub of water for a period of time.
This article presents the results of these studies, including the possible health benefits and risks of hot and cold showers.
Benefits of cold showers
Although a cold shower may not be pleasant, it can have some health benefits.
Reduce inflammation and swelling
Reduce muscle cramps
An older study in 2000 looked at the effects of different water temperatures on the body’s responses. In the case of cold water, researchers immersed participants in water at a temperature of 14 °C (57.2 °F) for one hour. Participants experienced the following effects (some of which are not necessarily health-promoting)
increased heart rate and blood pressure
increased levels of the neurochemicals dopamine and norepinephrine
Decreased levels of cortisol, the “stress hormone.”
Some of the benefits of cold water immersion include
Improved blood circulation
Exposure to cold water causes blood vessels on the surface of the skin to constrict. As a result, blood flow is directed away from the skin surface. A small 2019 study found that a cold shower after exercise can improve overall hydration by cooling the body.
As blood moves away from the skin, blood vessels in deeper tissues dilate. This improves blood flow to the deeper tissues.
Reduced cortisol level
Cortisol is the “fight or flight” hormone that the body releases in response to stress.
Therefore, lowering the level of cortisol in the blood can help reduce stress levels. Researchers have observed that cortisol levels decrease when people take a cold water bath.
According to a 2014 study, exposure to cold water triggers an automatic pain response called stress-induced analgesia (SIA).
SIA is a reduced pain response during or after exposure to a stressful stimulus, such as immersion in cold water.
Reducing muscle pain and fatigue associated with exercise. An older study from 2009 examined the effects of cold water immersion on physical performance in athletes. After exercise, some athletes were immersed in cold water while others were immersed in warm water.
The researchers found no difference in subsequent physical performance between the two groups, nor in the amount of muscle damage or inflammation the participants suffered.
However, the perception of muscle soreness and general fatigue was significantly lower in the group that received the cold water bath. This psychological effect could be useful in athletic competitions.
The benefits of hot showers
Hot showers can also have health benefits. Some examples of possible health benefits include
Improved cardiovascular health.
As reported in a 2014 hydrotherapy analysis, hot showers appear to improve blood flow in people with chronic heart failure. This is due to a natural dilation of blood vessels when exposed to high temperatures.
A 2012 study examined the effects of bathing in hot water on arterial stiffness, which occurs when arteries become less flexible. Arterial stiffness plays an important role in cardiovascular disease due to atherosclerosis, which can lead to high blood pressure.
The study found that participants who immersed their feet and lower legs in hot water for 30 minutes showed a reduction in arterial stiffness. Participants who were not immersed in hot water did not show this effect.
Improved muscle and joint health
As mentioned earlier, hot showers can improve blood circulation and help relieve stiff joints and tired muscles. On the other hand, cold showers can reduce inflammation and relieve pain.
A 2017 study examined the effects of hot and cold therapies on osteoarthritis of the knee. Researchers divided 96 participants into three groups. A control group received only standard osteoarthritis treatment. The other two groups received standard osteoarthritis treatment along with heat or cold therapy.
The heat therapy group applied heat to the affected knee twice daily for 3 weeks, while the cold therapy group applied cold to the affected knee twice daily for 3 weeks.
At the end of the study, both groups showed a slight decrease in pain and a slight improvement in knee function. However, these effects were not significantly greater than in the control group.
Improved brain health
A 2018 study examined the effects of hot water immersion on brain-derived neurotrophic factor (BDNF). BDNF is a protein that performs several important functions in the brain and spinal cord, including:
Promoting the survival of neurons
Promoting the growth, maturation, and maintenance of neurons
Promoting learning and memory.
The study was small and involved only eight men. One group took a 20-minute bath in hot water at a temperature of 107.6°F (42°C). The other group took a 20-minute bath in 35°C (35°F) water.
The participants who took a hot bath had significantly higher BDNF levels. The researchers concluded that the hyperthermia induced by the hot bath increased BDNF production.
Organizations such as the National Heart, Lung, and Blood Institute recommend taking a hot shower or bath before bed to improve sleep.
A hot shower can improve sleep quality because the body relaxes during the bath and body temperature drops afterwards.
When a hot or cold shower is appropriate
Doctors sometimes recommend hot or cold therapy for people with muscle or bone injuries. However, it is not yet known whether a hot or cold shower has the same effect as an ice pack or heating pad.
Some people with arthritis appreciate hot showers in the morning because they make them feel more mobile. Cold showers, on the other hand, are beneficial for injuries with inflammation.
As for hot showers to improve sleep, a 2019 study found that the best time to take a shower or bath is 1 to 2 hours before bed.
People with eczema and other skin rashes should avoid hot showers altogether, as they can further dry out the skin.
Prolonged baths or showers that are too hot or too cold can cause an excessive drop or rise in body temperature.
If a person’s body temperature drops below 89.96 °F (32.2 °C), the person may experience
decreased respiratory rate
a drop in blood pressure
Water that is too hot can cause burns and heat stroke.
If extreme temperatures are avoided, hot and cold showers can have some health benefits. Hydrotherapy is generally a safe strategy and does not cause dependence or significant side effects.
More studies are needed to investigate and confirm the long-term effects of hot and cold showers.