Expert reveals why cold showers on hot days could kill you

Daily Mail​

25-06-2025

The first big heat wave of the summer has sent millions in the US looking for a way to cool down, but one expert says taking a cold shower could be a fatal mistake.
A massive heat dome has trapped hot and humid air over more than half the US for days, sending June temperatures into triple-digits for the first time in decades for several major cities.
Professor Adam Taylor from Lancaster University explained how trying to cool your body down by jumping into very cold water actually has the opposite effect.
Instead of getting your body to release excess heat, suddenly shocking the body with a cold shower tricks the human body into thinking it should keep the heat trapped inside.
According to Taylor, this can be deadly for people with high blood pressure and heart conditions.
Moreover, there's a risk of organ damage when the body stays too hot for too long.
While these events tend to be rare, there's an extremely common problem that washing in cold water can exacerbate - body odor and unclean skin.
So, while a plunge into cold water may feel like relief in a heat wave, it might actually not be helping the human body at all.
Our body's optimal temperature is around 98.6°F. This temperatures ensures our body systems can function properly.
When the core gets too hot, the temperature regulating center of the brain starts sending nervous signals out to the blood vessels and muscles in or near the skin – telling them to start activating their cooling mechanisms.
If our core stays at high temperature for too long (around 102.2-104°F), this can lead to organ damage. So to ensure our temperature stays optimal, the body uses multiple techniques to cool itself down.
For instance, the body radiates heat into the surrounding environment by electromagnetic (thermal) radiation. Approximately 60 percent of our body heat is lost this way.
Sweating is another mechanism the body uses. Around 22 percent of our body heat is lost this way.
When the air temperature around us exceeds our body temperature, sweating becomes the dominant mechanism for reducing core temperature.
Any remaining body heat is then lost through a mixture of convection into the air or liquid the body may be in contact with and conduction into solid objects that the body may be in contact with.
To support these mechanisms, our blood vessels change diameter. The ones closest to the skin dilate (widen) to allow more blood into them so they can get close to the relatively cooler surface of the skin.
The body then works to circulate the blood so that heat from inside the body can be moved to the periphery to cool off. Similarly on our skin, the hairs remain flat to allow air next to the body to cool and be replaced, helping to dissipate heat.
Cold shower?
Of course, when the weather gets really hot outside, these biological mechanisms just don't feel like they cut it.
Although diving into a cold bath or shower straight after being out in the heat might feel nice on your skin, it isn't doing what is needed to reduce the core temperature of the body. It might also be risky for some people.
When exposed to cold, the blood vessels near to the skin constrict – reducing the blood flow into these areas.
So, in the context of cooling the body down, jumping into a cold shower does the opposite of what needs to happen, as less blood is now flowing to the surface of the skin.
This will hold the heat in and around your organs instead of getting rid of it. Basically, you're tricking your body that it doesn't need to cool down, but actually needs to conserve heat.
Depending on how cold your water is, sudden exposure could even trigger dangerous consequences for some people.
Exposure to cold water that is around 59°F can trigger the cold shock response. This causes the blood vessels in the skin (those in contact with the cold water) to constrict rapidly.
The shock increases blood pressure as the heart is now pumping against increased resistance.
This response can be particularly dangerous in people with underlying heart conditions, such as coronary artery disease.
The cold shock response can also lead to an irregular heartbeat and even death when going from very hot to cold.
Thankfully, these events are rare – and probably won't happen if you're just taking a cold shower or bath in your home. However, you might want to skip the cold plunge or avoid taking an ice bath on a hot day for this reason.
Hot showers are also a bad idea on a warm day. Although it's sometimes said that a hot shower helps the body cool down faster, this unfortunately isn't true.
Water that is warmer than the body is going to transfer energy in the form of heat into the body. This again prevents the body getting rid of heat – potentially increasing its core temperature.
On a hot day, a tepid or lukewarm bath or shower is the way to go, evidence suggests 78.8-80.6°F is most effective. This helps bring blood to the surface to cool, without being cold enough to cause the body to think it needs to conserve its heat.
Another reason to skip a cold shower on a hot day is that it might not help you get clean.
When we get hot, we sweat – and this sweat mixes with sebum, another skin product and the bacteria on our skin, which produces body odor.
Cold water has been shown to be less effective at removing and breaking down sebum and other debris on the skin, compared to warmer water, which means bad body odor will persist.
Cold water also causes the skin to tighten. This might potentially trap sebum and dirt within the pores, leading to blackheads, whiteheads, and acne.
However, warm or lukewarm water can help dissolve and loosen material in the pores.
As you plan your escape and recovery from the heat this week, a lukewarm or cool shower or bath, rather than a cold shower, is a safer and more effective choice. This will allow your body to dissipate heat away from your core without harm.
Equally, if you do feel the need to go cooler, do it gradually so you aren't shocking the body's automatic temperature regulation system into action.
Turning the temperature down gradually if you want to go cold, or slowly placing an arm or leg in at a time can help with this process.
This article is adapted from The Conversation, a nonprofit news organization dedicated to sharing the knowledge of experts. It was written by Adam Taylor, a professor of anatomy at Lancaster University.