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What's Typical?

6 December 2005

I sweat, you sweat, we all sweat. If we didn't we'd be in big trouble, however for a long time I've wondered how much is typical. Not long ago I saw a woman on a game show and she had large perspiration stains on her shirt. I could never be on a televised a game show, under the hot lights, with the emcee asking me trivia questions, because the flood from my underarms would wash away the contestants, the set and the audience. OK, so I exaggerate, but only a little.

Since my problem HH area is underarms, I want to know how much the typical person sweats there while under some stress, say during a job interview. How do my prodigious armpits compare? A web search turned up very little information, and the only data I did find discussed the maximum amount people can sweat from their entire body: 50 ml per minute. I do a bunch of tech writing for a living, but I hadn't the slightest idea how much that was.

With more sleuthing I converted 50 ml into a more familiar number 10 teaspoons. Is that a lot? Remember, that's from the whole body, not just the underarms. So how much do I sweat? I got so curious that from the hamper I pulled a blouse I managed to soak when I wore it while visiting my new inlaws on Thanksgiving. Stress always does it to me! There was a light salt ring left behind that measured at 10 inches across. But how much sweat is that? I used a measuring spoon to apply a half teaspoon of water. It turns our that's a lot of water, it spread 3/4rds of the way out. Another half teaspoon was enough to wet it as much as my underarms had.

When I'm under stress, I've known my underarms can go from dry to a 10 inch wet spot in about 15 minutes. So that's a mere 1 teaspoon in that time, which is nowhere close to 10 teaspoons per minute that some construction worker on a hot day might generate over his whole body.

I told Kevin about it (he's wonderfully supportive about my HH) and he said I had to figure in how rapidly the sweat dried. He suggested an experiment, which I'll describe below. I took 4 blouses of different fabric from my hamper: 100% polyester, silk, rayon and cotton. I proceeded to apply a half teaspoon of water to dampen the tummy area of each, measured how big the wet spot was, then I donned it to see how quickly the heat of my body dried it. Here are the results:

polyester	7 inches		16 minutes
silk		6 inches		19 minutes
rayon		5 inches		44 minutes
cotton		4 inches		53 minutes

I was astounded by the difference! The cotton took more than 3 times longer to dry than the polyester! I knew there was a reason I preferred poly and silk over rayon and cotton for tops. When I'm at work dealing with one situation after another, some sort of stress as simple as answering the phone makes me sweat for awhile. If that happens once every hour or so, a poly or silk item of clothing has time to dry, but a rayon or cotton one stays damp all the way until the next stress hits me. That explains why when I wear cotton it seems like my underarms are constantly damp. I think the wicking action of the poly helps to spread the wetness out and let it dry more quickly, which is also why it is used in exercise clothing.

To my surprise, the silk dried almost as fast as poly. Silk has the reputation of permanent water spots. While it is certainly more delicate than poly, in my experience wet washing silk takes out spots provided I had not used antiperspirant. I think something in antiP chemicals damages silk.

With all these numbers I think I can figure out the amount my underarms perspire. The blouse I wore Thanksgiving is 100% polyester. I recall that once my sweat patches reached about 10 inches across, they stayed that way most of the evening. It takes 1 teaspoon of water to make a wet area that size, and since it dries in 16 minutes but I was keeping it damp, I must have been regenerating that much sweat. So each of my armpits were sweating about 4 teaspoons per hour. How that compares to other people I still have no idea, but at least now there is some data, and the techie part of me can rest.

PostScript

Wouldn't you know, the day after I post the above I find some stats online. According to this site "each armpit has about 25,000 sweat glands, which can in total produce about 1.5 ml of sweat every 10 minutes." That's 9 ml per hour, or almost 2 teaspoons per hour, which is only half of the 4 teaspoons I seem to output easily. Under heavy stress I have soaked a shirt down to my waist and through a suit jacket, which might be 8 or 12 teaspoons per hour.

Perhaps their numbers are for the typical person rather than someone with hyperhidrosis? Are those the average or maximum values? Hmm, one question answered, and two new ones generated.

For prior stories, see the archives.