Old Wives Tale - Fact or Fiction?

I heard that jumping into the pool after getting really sweaty is bad for you. The same goes for turning down the A/C after getting sweaty.

The logic goes like this:

  1. You exercise, and your pores open and sweat is released
  2. When you jump into the pool or turn on the A/C, your body is chilled
  3. As a result, your body closes your pores
  4. This is problematic because while waste products are being released through your pores as sweat, your pores are closing, and these waste products get trapped.
  5. As a result, you get acne and other skin maladies from waste products’ being trapped near the surface of your skin.

Truth or tall tale?

Sounds like a myth to me. While I’m sure there are exceptions, acne generally stems from problems with sebaceous (oil) glands associated with hair follicles, not sweat glands. Sebaceous glands secrete lipid-rich, nutritious oils that bacteria can gorge themselves on. Sweat glands secrete mostly salt water, which bacteria would have little use for.

There are good reasons to be careful about rapid temperature changes after exercise - a rapid change (drinking very cold water, immersion etc) can trigger the Vagus reflex, causing the heart rate to drop, maybe even syncope (fainting).

As for skin infections etc - again, open pores can provide a path for bacteria, leading to rashes. Aftershave is supposed to disinfect the skin and close the pores after you have scraped them open and pushed bacteria round. I have never used aftershave and don’t have too many shaving problems. This is not likely to be the case when you have exercised. However, I would cool down a bit before hitting the water, particularly if it was not necessarily clean fresh water (lake or pond, as opposed to salt or chlorinated).


Me and a few million other Finns jump into cold lakes directly from hot saunas all the time and I haven’t noticed us suffering from skin maladies any more than other cultures. Sounds like hogwash to me.

I’m not an authority, but I find it hard to believe that your pores close so tightly that all waste products get trapped. Besides, what if you jump into icy water, and your pores close, but you exercise vigorously, so your body heats up again? Do your pores then open because your body’s heated up? Do they stay closed because the water’s cold? Or do they go insane like the machines in Star Trek when Kirk talked them to death?

If your body needs to sweat to induce cooling, it will. If this requires pores to ‘open’, they will.

Unless you are broken.

If you are sweating and jump into cold water, I’d think the natural, initial reaction might be to react and slow down the sweating process as this would only make sense. But, just like playing a very cold winter spot, if the need to sweat is there, you will sweat – cold temps be damned.


I was unaware that we use sweating to rid the body of waste products. What is the mechanism by which waste products get into the sweat glands?

They don’t. Also sweat glands are not ‘pores’.

There is some truth to it, but the actual reason is much different. You know how your voice sounds different to you? It’s because part of the sound is being transmitted through your body. Now imagine millions of tiny pores slamming shut in unison–you could go deaf!


Ironically, the problem with acne is what stuck in your skin.

Pores do not “open” and “close” or change size. Pores can become blocked with a mix of sebum (skin oil) and keratin (bits of dead skin cells), which is then called a blackhead or whitehead, comedone, pimple, or acne. It is possible to unblock such a pore, but it stays the same size whether blocked or not. Pores do not need to “open” to secrete sweat or sebum.

I was under the impression that hot water make your pores bigger. What’s actually happening when you rinse your face under hot water?

But it IS bad for others who get in the pool after you, and swim in water contaminated with your sweat.