How do antiperspirants keep you from sweating?
At the premiere of her 2014 movie "The Other Woman," actress Cameron Diaz garnered a lot of media attention — not so much for her role in the film, but for a startling admission about her personal hygiene.
"I don't believe in antiperspirant," explained Diaz in an interview with E's Marc Malkin. "It's really bad for you. I haven't used it for almost 20 years." Instead, she argued, people should just "let it go and trim your armpit hair so that it doesn't hold onto the scent."
The Huffington Post, one of the publications that jumped on this momentous scoop, snarkily noted that Diaz's avoidance of antiperspirant might explain those red-carpet photos of her with conspicuous sweat stains, as well as persistent gossip that she might have "issues with body odor" [source: Marcus].
But while the Hollywood star might blithely spend her days sporting au naturel armpits, most of us aren't so self-confident about our body's natural cooling mechanism and the aroma it can cause, if allowed to operate unhindered. More than 90 percent of American teens and adults use sprays, solid stick or roll-on products containing antiperspirants (which limit perspiration) or deodorants (which mask its aroma), according to a 2012 study by Mintel, a market research firm [source: MarketingInsight350]. We're so obsessed with preventing sweat stains and stinky armpits that it's become an $18 billion industry worldwide [source: Everts].
However, since most people don't engage in activities where they work up a sweat, dermatologists say that we don't need as much antiperspirant as we think. Bathing and changing clothes regularly will reduce the presence of the bacteria that create body odor [source: Toedt et al.] Dermatologist Dr. Jeanine Downie even told The New York Times that most people would "probably be fine just using a little powder."
It's safe to say that the science that prevents us from becoming sopping wet is a mystery to most of us who aren't chemists. But there's no need to break a sweat about it. In this article, we'll explain how antiperspirants inhibit perspiration.
Is It Really Possible to Prevent Sweating?
No, and you wouldn't want to, either. Perspiration is a natural body function, regulated by your autonomic nervous system, which helps the body regulate your temperature by releasing a fluid made up of water, sodium and other substances, which evaporates to cool you [sources: Medline Plus, MIT School of Engineering]. Sweating is so important to your body that it has about 2 to 5 million sweat glands all over its surface, which pump out several liters of perspiration each day [source: Moninger].
Instead of shutting down the perspiration process entirely, what antiperspirants aim to do is control it in certain areas — like your armpits and groin — that are especially prone to be stinky. These areas are equipped with a special type of sweat gland called apocrine glands, which form around hair follicles [sources: Hansen, Williams and Schmitt]. The apocrine glands kick into gear during puberty and are stimulated by stress or excitement as well as heat [source: Grossman].
The yucky smell that we associate with underarm perspiration actually is caused not by the sweat itself, but by bacteria and other microorganisms. They feed on the perspiration and produce waste byproducts such as trans-3-methyl-2-hexenoic acid, which cause the distinctive odor we all abhor [source: Everts]. The armpits, which are covered most of the time, are a great medium to grow those microbes [source: Ramirez].
Since the late 19th century, when chemists first started tackling the problem of body odor, there have been two primary solutions. One is to mask the stinky smell with a more pleasant aroma. The other is to use chemicals to actually inhibit the release of sweat from our skin's pores, to starve those stink-producing bacteria of food. In the next section, we'll explain how that works.
The War on Perspiration
In the late 1880s, various chemists got the idea of using aluminum salts in an effort to stop the flow of sweat from our armpits. How this actually works is kind of ingenious. Sweat, as it turns out, is pushed out of our pores by pressure created by charged particles, called ions, which want to move and join with particles of the opposite charge. But if you apply aluminum salts to the armpits, the opposite occurs, and your body draws ions from the antiperspirant into the pores, where they form plugs, which block the flow of water to the skin [sources: Williams and Schmitt, Newman].
The first trademarked product to exploit this phenomenon was a liquid called Everdry, which appeared on the market in 1903. Users applied it with a cotton ball, which was a bit messy. Another breakthrough antiperspirant was Odorono, a liquid preparation, which contained aluminum chloride. It was so effective that it actually reduced perspiration by about 60 to 70 percent, and lasted for up to three days [sources: Laden; Everts]. But it had a few downsides, too. It contained an acid that irritated the skin inside users' armpits, and sometimes even ate through their clothing [source: Everts].
Fortunately, antiperspirant makers have refined their formulas considerably since then, so they're less harsh. The trade-off is that the modern antiperspirants are actually slightly less effective — generally decreasing perspiration between 30 and 50 percent in the course of a day. While that may not seem so great, it's enough to prevent sweat from seeping into a person's clothing and creating conspicuous stains [source: Laden].
Cameron Diaz isn't the only person who worries that antiperspirants are somehow bad for your health. The Internet has been rife with rumors that the aluminum in antiperspirants can increase the risk of breast cancer and Alzheimer's disease, if it is absorbed by the body through a cut in the skin [sources: Grossman, Moninger].
But the National Cancer Institute says it is aware of no studies that conclusively link aluminum in antiperspirants to breast cancer, and the Alzheimer's Association says that studies have failed to confirm a link between the disease and everyday exposure to aluminum. Similarly, the rumor that chemicals called parabens, which have been found in breast tumors, are linked to antiperspirant use turns out to be shaky, since most major brands are paraben-free [source: Moninger].