Water Absorption during Shower?

I was sitting with some coworkers waiting for a meeting to start when someone mentioned that they had quit drinking coffee a few weeks ago and that they were feeling “dehydrated” all the time. (They had been a heavy coffee drinker so they figured that by not drinking coffee they were consuming a lot less liquid than they used to).

Since I had always thought that coffee was a diuretic, which would presumably dehyrate someone, I was a little surprised to hear this but before I could chime in someone else suggested that this person take a shower to “rehydrate” themself. Before I could ask how they could do this someone else mentioned that taking a shower is equivalent to drinking 6-8 glasses of water.

I had taken a number of physiology classes in college and I was pretty sure this was compeltely bogus but somone else chimed in that they had read the same thing somewhere. I never thought of our skin as some kind of sponge and that water would pass through into our cells at anything like that kind of rate.

So are these people crazy or do you really absorb large amounts of water when you take a shower, take a bath, go swimming etc? I just can’t believe that it really happens…

They are nuts. Not an expert at this but I do know that although your skin’s outer layer’s can absorb water (that’s why your fingers get pruny) you can’t absorb water into your bloodstream that way. Taking a shower or bath, or swimming are in no way equivalent to drinking water.

BTW caffeine is a diuretic, although I don’t know if the diuretic effect is large enough to cancel out the fluid you drink when you have a cup of coffee.

Most regular caffiene (and alcohol) drinkers get relatively immune to the diuretic effects of their chosen substance.

I have no idea, but just want to point out that your username/post combo made me smile. :stuck_out_tongue:

Oh, and just to re-iterate CookingwithGas’s point: One does not absorb any significant amounts of water into one’s circulatory system via the skin.

You work with a lot of people that need to join this board and read Snopes. :wink:

A few weeks ago, out of idle curiosity, I weighed myself before and after a shower. According to the scale, which is a digital model that rounds to the nearest 0.5 lb, the shower added half a pound. “Really?” I thought, and tried it again the following day. No difference. Ditto the day after. I concluded that the shower does add a small amount of weight via absorption, but less than half a pound, and that my initial measurement was a result of rounding: say, X.2 before, rounded to X.0; X.4 after, rounded to X.5.

So there you go, actual data. :slight_smile:

Given that 6-8 glasses of the stuff would weigh at least a couple of pounds (1 liter = 1 kilogram), I think the co-worker’s statements don’t hold, well, water.

Or it could be adhesion. Did you dry yourself thoroughly, including your hair, before making the “after” measurement?

Half a pound seems a lot. Could it be most of that weight is in your wet/damp hair? - It’s a shame I have no scale.

Unfortunately, here’s some more data: I just weighed myself on a (0.1 lb resolution) digital scale five times, about twenty seconds apart. I got a range of 1.9 lbs, and I’ve gotten larger ranges in the past on consecutive weighings - depending mainly (I think) on where exactly I place my feet on the scale.

But even if we assume that Cervaise is gaining weight in the shower (and not, say, showering with snack foods), I think that I’d be more inclined to guess that hair is absorbing (weighable quantities of) water than skin.

Heh - three brilliant minds, all thinking alike in suspecting hair, within three minutes!

Not wholly off topic, but it always seems to me that swimming (whether in a pool or the ocean) makes you need to pee more. Anyone else notice this? It’s tempting to think you’re absorbing water through your skin, but I suspect in reality that being in the water inhibits sweating, meaning that wastes need to come out through your urine, rather than your skin. I could be wildly off the mark, but for the moment, I’m clinging to my illusions.

What about inhaling water vapor during a hot shower? I mean, the weight would probably be negligible, but that would at least be additional moisture entering your bloodstream. Or not?

Wait, were your co-workers implying that the decaffeinated co-worker hadn’t had a shower in the several weeks since he’d given up coffee? Doesn’t he presumably take showers often enough that he’d already have solved the problem?

The coworker who complained about being dehydrated wasn’t one of the ones that claimed taking a shower would hydrate you. In fact they were just as perplexed by the whole thing as I was :rolleyes: .

If it was true that a shower would re-hydrate you wouldn’t it make sense that during the winter when the air is dry and your skin is dry that a shower would re-hydrate your skin. On the contrary a shower actually makes your skin dryer.

Ask an olympic swimmer if they need to drink anything during practice to stay hydrated? Or does just being in the pool keep them hydrated just fine?
I’d vote for they have to drink something.

I’d think any water you absorbed into skin to make it pruny, and any water vapor that condensed into your lungs, would have to increase your hydration via the bloodstream. All these cells are drifting around equilibria and sharing fluids with the bloodstream. But I bet it isn’t much, maybe a few ounces for a long exposure.

A shower would also affect your sweating and the water loss associated with humidifying breath. Preventing a few ounces of loss must be somehow equivalent to gaining a few ounces.

I read somewhere that you can get as much as 10% of your oxygen by absorption through the skin, which makes me wonder whether a special dermabrasion and cold oxygenated water soak (or some such) could be supplemental therapy for someone in respiratory distress. And of course there are many drugs and poisons you can absorb through the skin. Sounds reasonable (though maybe small) to me.

I suspect that the real reason is that the cold water makes you pee more, because the body reroutes more blood to the internal organs, including the kidneys to save heat.

Sorry, untrue. We breath thru our lungs. NOT our skin.


I’ve been working out for a year now. Went from 235 pounds to my current weight of 188 (depending on how hydrated I am).

This morning, I weighed myself after my “morning constitutional” and before my morning 5 mile run. I weighed 186.5.
Then I ran 5 miles.
Weighed myself again and I weighed 185.5- a loss of one pound.
I then showered. After showering, I weighed myself again…
188.5 pounds!

So either my digital scale is whacked, or…

One gallon of water = approx. 8 pounds.
There are eight pints to a gallon, so a pint of water weighs 1 pound.

It is wholly conceivable that I sweated a pint during my 5 mile run. That would explain the weight loss of one pound.

Important to note:
After sleeping through the night, I assume my body dehydrates, as I’m simply not taking in any water while sleeping. SO in the morning, I’m dehydrated.
I don’t drink any water before my run, because I can’t run far with anything in my stomach. Also- I’ve dropped whatever weight in urine and feces before my run, dehydrating myself further. Not to be gross, or risking TMI, I urinate at least a pint, and without TOO much investigation, I’d estimate that I drop at least a quarter pound in feces.

So I’m dehydrated with clear bowels at the start of my run.

The three pound of gain after showering MUST be from water absorption during my shower. In this morning’s case, I took a cool, prolonged shower (just to address the water vapor issue).

My scale is a reasonably accurate standard bathroom digital scale. No matter where I stand on it, it rests the same weight.

So my dehydrated state caused my skin to be dehydrated, and I must have absorbed three pints of water during my shower!

Three pints sounds like a lot, but I don’t think my scale lies…

My 2 cents.