Talk:Perspiration

Do we have any information about the potentially attractive nature of sweat - is sweat used to attract mates (talking from a more historical perspective here)? Tompagenet 10:43, 23 Aug 2003 (UTC)

Pheromones are present in sweat. --Dante Alighieri 10:45, 23 Aug 2003 (UTC)

Salty!

OK, I don't know if anybody else was puzzling over this, but I was wondering why sweat is salty -- you need those salts, and companies like Gatorade do good business selling you a way to put salts back in when you exercise. Why don't you sweat plain water?

I found an answer here, from Dr. Stephen Cheung (it's the second interview; direct link to MP3).

If you can't listen to the sound file (it's not very long), the short version is:

your sweat glands get the fluid, indirectly, from the plasma in your bloodstream
the fluids in your body are naturally salty
as you may have suspected, there's no advantage to sweat being salty, so...
your sweat glands also act as a filter to try to keep the salt in your body; that is, sweat is *less* salty than what's in your body... Did you know that dried sweat can be mistaken for dried chicken urin? If not thats because only scientists know that, but now so do you.

Neat.

Disclaimer: I'm not a doctor, and everything I know about this, I know from that link.

Untrue. I tasted some normal saline a few days ago. Much less salty than the sweat of my brow. Sweat is salty so it evaporates quicker and cools the skin more rapidly. JFW | T@lk 10:03, 15 Apr 2005 (UTC)

According to the saline page, saline has the same osmolality as blood. Plasma (which Dr. Cheung says eventually becomes sweat -- you're not sweating red blood cells) makes up only half of your blood, and it's the half with the salt, so it should be about twice as salty as saline. I don't think the fact that saline tastes less salty than sweat negates anything I said (or heard).

Also, IIRC, you've got it backwards: salt water evaporates more slowly, not more quickly, than fresh water. (A web search seems to confirm this -- here, here, or here.)

I gladly admit that it's possible Cheung's explanation isn't correct, but it sounds reasonable to me, and I'm not yet convinced that it's untrue.

Good sources; normally, the internet is lousy as a physiology source.

It could actually be that the whole purpose of sweat saltiness is to delay evaporation, i.e. to prolong its effectivity to stave off heat. You could be correct that sweat is less salty than blood: sweating gives a reference of 35-65 mmol/L sodium, which is much less than the serum sodium content of 135-145 mmol/L (which, incidentally, is serum so with the blood cells removed).

Furthermore, to sweat water without electrolytes would damage the body's internal milieu: hypernatremia (high sodium load) would be so severe the kidneys would lose their concentrating ability, leading to paradoxical excessive fluid loss through the renal tract in addition to the cutaneous losses. JFW | T@lk 09:41, 17 Apr 2005 (UTC)

Sweating is also the practice of employing women and children in low-wage professions that require long hours of tedious efforts without relief. May 3rd, 2005 23:54 Z

The body moves water mainly by pumping salts, water follows the salt because of osmotic pressure. Sweat at the base of the sweat gland has the same amount of salt as blood, but as the sweat moves up the sweat gland tube some of these salts are reabsorbed. At higher sweat rates a lowere percentage of salts are reabsorbed.

normal sweat response

When exercising it is normal to start sweating at the forhead then down the rest of the body. Is it normal to sweat more a few minutes after one has completed exercising than one did while working out?

toxins

there are a lot of claims all around that sweating carries toxins from the body. most commonly, from the armpit, groin, behind the knees and ears. i can't find any information on this. what do you guys know? Dreamer.redeemer 08:58, 21 January 2006 (UTC)[reply]

i've found no information whatsoever on this. perhaps they were misinformed and thought sebum was a toxin. i think it's safe to say there are no toxins in sweat anywhere on the body. Dreamer.redeemer 04:26, 31 January 2006 (UTC)[reply]

Sweating is a good thing apprectiate it for what it is.

It's spin from sauna freaks. JFW | T@lk 22:21, 31 January 2006 (UTC)[reply]

Contradiction in the articles on Urea and Sweating

I hope this is the right place as well. This is my first comment.

There is a contradiction between the entries on Sweating and Urea.

The article on Sweating states that "Sweating (also called perspiration or sometimes transpiration) is the production and evaporation of a watery fluid, consisting mainly of sodium chloride (commonly known as salt) and urea in solution, that is secreted by the sweat glands in the skin of mammals."

The article on Urea states: "Many researchers used to believe that a small amount of urea was excreted (along with sodium chloride and water) in human sweat. However that was proved wrong when Dr. M. Falk determined at RC Institute that only sodium chloride and water are excreted from sweat.”

I don't know for sure which is correct but sweat either contains urea or it does not. Whoever wrote the paragraph at the article on Urea seems certain that sweat does not contain urea while the article on Sweating states that it does.

I have left this same comment at both articles on Urea and Sweating.