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Sweating - an overlooked but natural way of beating the heat

By Eric Adler
Knight Ridder News Service

    You know what a heat wave means. Dripping, beading, and vastly under appreciated sweat.
    Yes, under appreciated. Because while sweat may seem bothersome, without it every one of us would be melting like a Salvador Dali pocket watch.
    In fact, if sweating doesn't do it's job and your core body temperature rises beyond 105 degrees, you're talking kidney dysfunction, muscle breakdown, disruption of brain functions, and even death.
    Which is why the human body employs all the processes at it's disposal to stay close to the temperature at which it best runs: 98.6 degrees.
    Exercise, contract a fever, stand in the summer sun, do anything to increase the body's temperature just a fraction, and you'll quickly appreciate how reliable the body's five million sweat glands are.
    In more detail, here's how our bodies handle the heat:

•  Nerves called thermoreceptors inside the body and on the skin signal the brain to a rise in temperature.

•  In the brain, the hypothalamus is the body's thermostat. When body temperature rises above 98.6 degrees, the nervous system reacts to get rid of the heat.

•  Flushed skin: Blood vessels dilate, opening up like big pipes, rushing more blood to the skin's surface, causing more heat to escape.

•  Sweat glands pump perspiration through pores. Cooling occurs when body heat is transferred to the sweat, causing it to evaporate and carry heat away, cooling the skin. Dripping sweat means perspiration can't evaporate fast enough.

•  Sweat is 99 percent water and 1 percent dissolved substances such as salt.

•  About a pint of water is lost through the skin in normal conditions, although as much as three gallons can be lost in a day because of exercise or hot weather. That's why staying hydrated is vital.

•  The body's five million sweat glands are packed so tight that a green pea placed on the skins surface would cover more than 100.

•  Sweat itself is odorless. A reaction with bacteria produces odor.

•  Aluminum and zirconium salts in antiperspirants react with sweat to create a plug that stops up the sweat gland. They also contain some anti-bacterial agents, as do deodorants, which are mostly perfume. The best roll-on and soft-solid antiperspirants reduce sweat output by about 50 percent; sticks 25 to 45 percent; aerosols 25 to 35 percent.

•  Facial sweating from spicy foods comes from capsaicin, a component in the food that stimulates nerves in the mouth that usually respond to rises in temperature.

•  When comfortable and at rest, the body typically gets rid of about 60 percent of excess heat via infrared radiation. Heat travels from the skin to cooler surrounding objects. It's when the body heats up that sweat and evaporation become more vital.

•  Humidity: The body stays hot because the air is already thick with water vapor. There's little place for evaporated sweat to go, so the rate of evaporation slows. Since it's evaporation and not sweat, per se, that cools the skin, the skin stays hot and wet.

•  Danger is at hand if someone suddenly stops sweating in hot weather. That means the body is in shock, preserving water and going into possibly fatal heart stroke.

•  Some people are born without working sweat glands. The condition, hypohidrotic ectodermal dysplasia, is rare, inherited and incurable. It also produces dry skin, wrinkled skin, sparse dry hair, small brittle nails and cone-shaped teeth. Reduced activity is the most common treatment.

•  Hyperhidrosis is a socially embarrassing disorder that causes people to sweat excessively, especially from the arms, feet and hands, even in normal conditions. The use of botulism toxin, or Botox, to paralyze the sweat gland is the most recent effective treatment, lasting up to six months, after which new nerve endings grow and the treatment must be repeated.

Reprinted with permission of Knight Ridder/Tribune Information Services.

From the Philadelphia Inquirer - Monday, August 2,1999.