A cool shower promises vigor and a strong immune system. While the body shivers, a chain of powerful reactions is initiated inside. Therapist and cardiologist Andrey Kostikov told “Rambler” what happens to the body under a cool shower, whether this habit can prolong life, and for whom it is undesirable. What happens to the body In the first few seconds, the body experiences cold shock. A person takes a reflex breath, blood pressure rises, and hyperventilation of the lungs begins — this is the so-called cardiorespiratory response. Then, the sympathoadrenal system is excited — the connection between the sympathetic nervous system and the adrenal medulla. At this moment, the volumes of neurotransmitters and the hormones norepinephrine and dopamine increase in the blood. An experiment at Charles University showed that when immersed in water at 14°C, norepinephrine levels increase by 530%, and dopamine by 230%. Over time, the body adapts to the cold shock, so for those who practice cold showers or winter swimming, cardiorespiratory reactions are no longer as pronounced. Benefits of a cool shower A cool shower is recognized as far cryotherapy along with winter swimming and dousing. The health benefits of such procedures are ambiguous, although there are some advantages. “From the standpoint of evidence-based medicine, cold and contrast dousing is a form of mild physiological stress that can initiate certain adaptive processes in the body. First and foremost, regular exposure to cold trains the thermoregulation system and reduces sensitivity to cold.” Muscles A cool shower slightly helps muscles recover after workouts. A 2021 Cochrane review including 17 small, low-quality studies showed that immersion in cold water reduces muscle soreness and fatigue. However, the optimal water temperature and duration under the shower are unknown. It is impossible to give practical recommendations based on these findings. Immunity Studies show that cool showers and hardening can affect some markers of immune function. For example, increasing the levels of monocytes, lymphocytes, and other immune cells. “There is evidence that repeated cold exposure can moderately enhance the immune response. Some studies link this to the activation of the sympathetic nervous system and the release of norepinephrine,” says the doctor. For example, an experiment in the Netherlands showed that people who practiced contrast showers called in sick less often. Three thousand people aged 18 to 65 participated in the study. For a month, one half took a cool shower for 30, 60, and 90 seconds, while the other half was a control group. Analysis showed that volunteers in the intervention group missed work due to illness 29% less often, but the habit did not affect the number of days of illness. It is likely that people accustomed to the cold cope with ARVI more easily due to reduced inflammatory reactions, but they get sick just as often and for the same length of time. Vessels and the lymphatic system Cold stimulates blood flow: the body tries to send more blood to the core to protect internal organs. The effect will be more pronounced if you take a contrast shower. “Alternating hot and cold water can be called a warm-up for the vessels. They alternately narrow under cold water and expand under hot water, which improves their elasticity and tone. This can help reduce swelling and a feeling of fatigue in the legs,” explains the cardiologist. But a cool shower won’t help remove toxins. “The liver and kidneys are responsible for detoxification in the body. Improved blood circulation can indirectly contribute to their work, but the effect of this is clinically insignificant. Direct ‘toxin removal’ through the skin does not occur with cold exposure,” the doctor replies. Metabolism During a cool shower, the body tries to warm up and increases heat production. Muscle activity (slight shivering) and brown fat, which burns glucose and releases heat, are activated. There is also evidence that winter swimmers have improved insulin sensitivity. This can be considered a prevention of type 2 diabetes and heart disease, although the level of evidence for such studies is low. A study by the National Institutes of Health showed that repeated immersion in cold water slightly reduces the amount of fat tissue in mice. However, these data cannot be extrapolated to humans, so it is premature to say that a cool shower helps with weight loss. “Cold can slightly increase metabolism due to the activation of brown fat, but this effect is too small to consider a cool shower an effective weight loss strategy. Without correcting diet and physical activity, one should not expect significant results,” the specialist cautions. Stress Cold triggers the release of hormones and neurotransmitters that are involved in the stress response and affect mood. A systematic review that included 11 studies with three thousand participants confirmed that stress levels decrease 12 hours after immersion in cold water. Men participating in the experiment also reported sleeping better after a cool shower. “Cold stimulation activates the sympathetic nervous system, leading to a significant release of norepinephrine and dopamine in the brain. This can cause a feeling of vigor, mental clarity, and improve mood,” explains Andrey Kostikov. A 2023 study also found that short-term full-body immersion enhances positive emotions and reduces negative ones. The authors of the article attribute this effect to the influence of cold on major brain neural networks. Lifespan Scientists have long studied the link between aging and the effect of cold. There is no reliable and specific data yet. In 2025, work from the University of Poitiers in France showed that in laboratory conditions, cold reduces chronic inflammation, enhances protection against oxidative stress, and improves metabolic health, which should theoretically affect aging processes at the cellular level. However, in practice, mortality and morbidity rates are usually higher in regions with cold climates. Therefore, how hardening affects aging and longevity in the long term is unknown. “Overall, a cool and contrast shower is a non-pharmacological tool to improve general tone, the body’s adaptive reserves, and mood. Such activities have a scientific basis, but their clinical severity ranges from moderate to insignificant. The effects appear with regular and correct use, and it is not a panacea,” the doctor concludes. Hardening and winter swimming: how cold water can help strengthen health How to take a cool shower You should start hardening with a cool shower gradually. First, short immersions of 30-60 seconds are recommended. Over time, this period can be increased to 5-10 minutes. As for the water temperature, no specific figures are given. Usually, studies use water temperatures from 10 to 20°C. “The first reaction to cold is to hold your breath, but you need to take slow, deep breaths, which helps the nervous system adapt. It is better to direct the stream first to the feet and hands, then to the large muscles (legs, back, chest), avoiding a direct strong jet on the head and heart area,” advises the cardiologist. Recommendations for a contrast shower are slightly different: Stand under a warm shower at a comfortable temperature for 2–3 minutes. Switch the water to cold, 10–20°C, for 15–30 seconds. Switch the water to hot, 38–45°C (but not scalding), for 1–2 minutes. “You can repeat the cycle 2–5 times. Always finish the procedure with cold water. You can take a contrast shower every day, preferably in the morning for vigor or after a workout for recovery,” says the doctor. Who should not take a cool shower A cool shower is not suitable for everyone. The main contraindication for such procedures is heart disease. A sudden immersion in water can provoke cold shock and trigger lung hyperventilation. Against this background, breathing and heart rate increase, and blood pressure rises. In people prone to cardiovascular diseases, this can cause arrhythmia. This primarily concerns patients with unstable angina, uncontrolled arterial hypertension, severe heart failure, and those who have recently had a myocardial infarction or stroke. “Peripheral vascular diseases: thrombophlebitis, severe atherosclerosis of the lower extremity vessels, and Raynaud’s disease are also contraindications for such procedures. Cold can provoke severe vasospasm,” interprets cardiologist Andrey Kostikov. You should also refrain from hardening during a cold or exacerbation of chronic diseases, such as pyelonephritis or rheumatoid arthritis. It is important to listen to your feelings and stop the procedure if the following occur: dizziness; difficulty breathing; rapid heartbeat; severe fright. What are the dangers of Epiphany bathing and what to do if you want to go into an ice hole Main points The benefits of hardening and a cool shower are ambiguous. There is evidence that such cryotherapy helps muscles recover after training, improves metabolism, and activates immune responses. However, these effects are moderate and insignificant. A cool shower is a safe procedure; the main contraindication is cardiovascular disease due to the risk of arrhythmia. The main risks are associated with immersion in open water; at home, the probability of negative consequences is low.
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