Personal Health : To Keep Your Cool,<i> Do</i> Sweat It

Think of it as central air conditioning for the body, especially during these dog days. If not for the impressive network of sweat glands in your body--the average person boasts 2 million to 3 million--maintaining a healthy body temperature would be impossible.

“Animals pant, humans sweat,” says Dr. Stephen Ross, UCLA assistant clinical professor of family medicine on staff at Santa Monica Hospital Medical Center. Sweat is a major help in controlling the body’s internal temperature, he says.

Under Your Skin

Sweat glands lay waiting to produce and excrete what polite people call perspiration, a mixture of mostly water with sodium and other substances. Sweat glands swing into action not only when you get too hot, but when you get tense.

“Sweat is controlled by the sympathetic nervous system,” Ross says. “That’s the involuntary nervous system, characteristically thought of as the ‘fight-or-flight’ reflex.”

Some sweat glands, like those on the palms and soles, open directly to the surface of the skin. Other sweat glands, like those in the armpits and genitals, open into a hair follicle and then reach the skin surface.

Heaviest sweat areas? Forehead, upper lip, neck, chest, groin and armpits. The places nervous sweat is most likely to drip from? Forehead, palms, soles and armpits.

Sweating Buckets

“A person can sweat up to a liter of fluid an hour,” Ross says. That volume usually accompanies high-intensity exercise. “But the average person probably sweats a quart or a quart and a half of fluid a day”--except under extreme weather conditions, like August in the Valley.

“As the temperature goes up we’ll sweat more to keep the internal body temperature regulated,” Ross says.

Who Sweats More?

Unfit people generally sweat more than fit people, Ross says. “Overweight people probably sweat more than average,” he says. “The extra weight produces more heat. Their body will sweat more to keep the temperature controlled.”

Kids usually sweat less than adults, he says. Their surface area is smaller, for one thing, and they have other cooling mechanisms, like increased breathing rates.

In a study published last year in the journal Medicine and Science in Sports and Exercise, McMaster University researchers compared sweat loss of young adults and children and found indeed that children had a lower sweating rate, even when their smaller body surface areas were taken into account.

The Odor Theory

When bacteria on the skin act on sweat, odor follows. But some people’s sweat smells much worse than others, Ross and Hayek agree.

“The theory is, some enzymes in the sweat have an odor,” Ross says. “Some people just have more of those enzymes.”

There seems to be no correlation between sweat volume and sweat odor, Hayek says: “I know people who sweat a lot and don’t smell and people who sweat a little and do.”

What you eat or drink might affect sweat smell, too, Ross says. Food and drink that increase blood flow to the skin--such as alcohol, spicy foods and even caffeine--could cause you to sweat more.

Sweat Glands Gone Wrong

In people over 60, the sweat glands have begun to degenerate, Ross says. As an aging person’s skin becomes thinner, the number of sweat glands decreases. To help control body temperature, he tells older people to pay special attention to fluid intake on warm days.

“If people are sweating extremely large amounts, they have to be sure they are replacing some of the sodium (along with the water),” Ross says, recommending that older people consider sports drinks, which replace both.

Adequate fluid intake is even more critical if it’s humid because humidity hampers the evaporation of sweat necessary for cooling.

No Sweat

Beware, Ross says, if you suddenly stop sweating but don’t feel cooled off. It could be a warning of heatstroke, the most serious kind of heat problem, which demands immediate medical attention.