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To outsmart sweat, it helps to know exactly what it does. When this mix of water, salt, and other minerals evaporates from your skin, it cools you down, allowing your body to maintain its core temperature. "There are two kinds of sweat: eccrine, a thin liquid that occurs all over the body when it's hot outside or when you exercise, and apocrine, a thick secretion found mainly at your underarms," says dermatologist Dee Anna Glaser, MD, president of the International Hyperhidrosis Society. Apocrine is tied to odor and is typically related to stress.
Although your diet, health, and emotions may play a role, how much you sweat is mostly determined by genetics, as is where you sweat. The most common spots are your underarms, palms, soles, and forehead because they have the highest density of sweat glands. (The underarm area is home to a bacteria that digests sweat and produces BO.) Sweat patterns are highly individual, however: For instance, your back might perspire first because the glands there are quickest to respond to your brain's signals in times of heat or stress, Dr. Glaser says.
But sweating isn't only about your DNA. "Part of how much we sweat is adaptation," explains James Winger, MD, a doctor of sports medicine at Loyola University Chicago Stritch School of Medicine. "People who are used to a hot environment sweat more efficiently, as do athletes, whose bodies have been trained to disperse heat quickly." He points to how runners prep for races like a marathon in Las Vegas by training in similarly hot conditions. Dr. Glaser agrees, adding that "if you acclimate like this for even two to three weeks, your body will learn to maximize heat release."How to Stay Dry
First, choose the right product: antiperspirant. Deodorants curb odor, not moisture; antiperspirant-deodorant combos tackle both. Some people opt for deodorant because their sensitive skin reacts badly to antiperspirants. Others avoid it because of rumors that aluminum-based compounds -- the active ingredients in most antiperspirants -- have been linked to cancer or Alzheimer's disease, but clinical studies show no evidence of such a connection. Whether you use a solid, a gel, or a roll-on doesn't matter, but the time at which you apply the stuff does: Derms recommend putting on antiperspirant before bed at night and then reapplying it in the morning for the best results. "For your antiperspirant to work, it has to get into the sweat glands and block them," explains David Bank, MD, a dermatologist in Mount Kisco, New York. "Overnight, you're calm and cool and your skin is completely dry, so a much higher percentage is going to be absorbed."
You can apply antiperspirant anywhere that sweat surfaces, but watch for irritation, especially on sensitive spots like your chest. For the area under your boobs, dust on baking soda when your skin is clean and dry. "Baking soda is antibacterial and anti-inflammatory. In addition to drying up moisture, it prevents irritation," Dr. Bank says. To absorb sweat on your scalp, use dry shampoo, and to keep feet dry, try sweat-wicking inserts like Summer Soles ($8, summersoles.com), Dr. Glaser suggests. To prevent down-there sweat, opt for an absorbent powder designed for that area. Your workout wear also makes a difference. Invest in high-tech synthetic fabrics that feel airy and wick moisture away from your skin.
If it takes you forever to cool down and dry off post-workout, jump into as cold a shower as you can stand. "Anything that lowers your core temperature will help you stop sweating sooner," Dr. Winger says. Short on time? Simply stick your feet under the spray. Humidity, which prevents sweat from evaporating, may also be part of the problem. The only real fix is to take it easy. "If it's a very humid day and you're out running, slow your pace," Dr. Winger says.
If you sweat a lot, doctors often recommend laser hair removal for your underarms. "I find that it leads to less sweat production and decreases odor too, because your hair accumulates more bacteria than your skin," says Mary Lupo, MD, a dermatologist in New Orleans. For people with hyperhidrosis, or excessive sweating, dermatologists offer more dramatic solutions, like prescription-strength antiperspirants, such as Drysol, which contain 25 percent aluminum chloride and are also effective on your palms and feet, or injections of Botox or Dysport, which temporarily deactivate your sweat glands. For smaller zones, like the underarms or hands, the injections cost about $1,000 for results that last six months to a year.
When the weather heats up, products that help keep you dry need to work overtime. We put the latest to the sweat test.
Secret Outlast ($5, drugstores)
It fights wetness and odor-causing bacteria for as long as 48 hours.
"It dries ultrafast, and I stayed sweat- and odor-free even through an intense run."
Dove Clear Tone Anti-Perspirant/Deodorant ($6, drugstores)
It uses calendula and other moisturizers to reduce dark marks caused by inflammation or dryness.
"I didn't notice a difference in my underarms' color, but the stick kept me dry all day."
Urban Decay De-Slick Oil-Control Makeup Setting Spray ($29, macys.com)
Microscopic cooling particles prevent makeup from melting.
"The mist dried quickly and stopped my foundation and mascara from slipping away."
MAC Cosmetics Prime Future Prep + Prime Skin Smoother ($30, maccosmetics.com)
Its velvety texture helps your skin look matte and flawless, and it fills in fine lines.
"It made my pores less noticeable and toned down shine along my nose, forehead, and chin."
Originally published in FITNESS magazine, June 2012.