When the heat is intense, many rush to jump into a cold shower to cool down. But it turns out that this immediate relief not only doesn't help — it can actually be harmful. Studies show that a cold shower on particularly hot days does not cool the body from the inside, and sometimes even makes the situation worse.
The Conversation explains that the optimal temperature of the human body is around 37 degrees Celsius. When core temperature rises to 39 or 40 degrees (which can happen during an extreme heatwave), there's a real risk of damage to vital organs. Therefore, the body activates various mechanisms to cool itself:
- Releasing heat into the environment through thermal radiation (about 60% of the heat)
- Sweating (about 22%)
- Losing heat through contact with cool air or cold surfaces
For all of these to work, blood vessels near the skin expand and bring the hot blood from the core to the surface. There, closer to the less-hot air, the blood cools and returns inward.
So what's the problem with a cold shower?
A cold shower does the opposite: The cold water causes the blood vessels to constrict and therefore prevents the hot blood from reaching the skin’s surface and cooling down. The result: The body “stores” the heat near the heart, brain, and other organs, which can be dangerous.
And in extreme cases? A water temperature of just 15 degrees Celsius can cause “cold shock” — an automatic reaction that causes a sharp rise in blood pressure and irregular heartbeat. For those suffering from heart disease, this can be dangerous, and even fatal.
Although this is a rare reaction, especially in a home shower, it's best to avoid an icy shower when it's extremely hot outside.
A hot shower isn't a good solution either: Hot water transfers more heat to the body and raises the core temperature, which is the opposite of what we need. Studies indicate that the ideal water temperature during hot days is between 26 and 27 degrees Celsius: Not too cold, not too hot — exactly what’s needed to allow the body to cool down safely and efficiently.
And there's another reason to skip the cold shower: It doesn't clean well. When we sweat, the body releases sebum that mixes with bacteria and causes body odor. Cold water is less effective at breaking down these layers, and sometimes even “traps” dirt in the pores, which can cause pimples or blackheads. Warm water, on the other hand, dissolves dirt much better.
So the next time you try to cool down — go for a lukewarm or mildly warm shower. If you still feel like having cold water — do it gradually, slowly, and carefully. That way, you'll give your body time to adjust and stay healthy even in a heatwave.