Science Questions

Can a person sitting in a bath dehydrate?

Wed, 4th Sep 2013

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Ahmed Youssef asked:

If one went without consuming water for three or four days but was submerged in fresh water for all that time, would you still dehydrate?






Ginny - The short answer is, no. Your skin is pretty waterproof. Thatís why we can go out in the rain and we donít get all soggy. Well, our clothes might, but our skin is actually pretty waterproof. Although, if you were in somewhere very, very hot, sitting in water might actually help stop you from dehydrating, just because it would keep you cool, so you'd sweat less. But you wouldnít actually be able to absorb it through your skin. Now, there's a group of researchers in Denmark who actually decided to test this, but rather than using water, they thought it would be a bit more fun to do it with vodka. So, they sat with their feet in a bath of vodka for a while and they tested their blood alcohol levels and they found that they didnít get drunk at all. So, that just shows that you're not absorbing things through your skin like that.

Chris - We did interview them on this programme, Ginny and they did say that duck in bubble bathalthough they didnít absorb any alcohol according to the blood test, they did all start talking very loudly and telling rather raucous jokes. So, it had a psychological effect if not a physiological one.

Ginny - Well, I wouldnít have been surprised if they'd inhaled some alcohol fumes and got drunk that way. Iíd be quite interested to know though if their feet went wrinkly because we all know that our fingers and toes go wrinkly in the bath. People used to think that that was because you're absorbing water through your skin. But actually, some recent research at Newcastle suggests that itís evolved to help us grip objects when our hands are wet. They think itís actually down to your nerves because if youíve got nerve damage, it doesnít happen. So, they found that people were much better at picking up marbles underwater when their hands had been in water for a while, so their fingers had gone wrinkly. So, it works a bit like the tread on tyres, but itís actually controlled by your nerves, not by you absorbing water through your skin.


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If it is a hot water, you can sweat while in water.
No significant amount of water from the bath would enter your body through the skin.
You obligatory lose some water by breathing and by urinating (at least about half a liter of urine per day even if you do not drink), so you would lose at least about 2 liters of water in three days, which means mild to moderate dehydration.
<(questionable) link removed> healthresearch, Sat, 24th Aug 2013

The question was whether it is possible to become dehydrated while submerged in water, so the short answer is 'yes', Ginny. Despite being submerged in water, your body would lose water that could not be replaced by absorption. Currently Clothed Scientist, Tue, 30th Dec 2014

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