Why taking cold shower on hot day might be bad idea

When the weather warms up, many of us use a nice cold shower to help us cool down. But while this might feel like relief, it might actually not be helping the body cool off at all.

Our body’s optimal temperature is around 37°C. But when the core gets too hot the temperature regulating centre of the brain starts sending nervous signals out to the blood vessels and muscles in or near the skin — telling them to start activating cooling mechanisms.

If our core stays at high temperature for too long (around 39-40°C), this can lead to organ damage. For instance, the body radiates heat into the surrounding environment by electromagnetic (thermal) radiation. Approximately 60% of our body heat is lost this way.

Sweating is another mechanism the body uses. Around 22% of our body heat is lost this way.

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. Now, diving into a cold shower 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 effectively hold the heat in and around your organs.