5 Fun Facts You Probably Didn’t Know About Body Odor and Sweat

5 Fun Facts You Probably Didn’t Know About Body Odor and Sweat
Photo: Getty Images/Allison Kahler

As someone who’s braved (and survived) seven summers on the New York City subway, body odor and sweat are things I am no longer grossed out by. Sure, they don’t feel or smell nice—especially when you’re trying to slide past someone in a very cramped space—nonetheless, sweat is the ventilation system our bodies need, and sometimes body odor is the by-product.

Now that we’re just a few weeks from what will likely be an unbearably hot season, you’re probably applying a few extra swipes of deodorant or deciding what your signature perfume will be. But even with those things, you can’t completely avoid a little BO or sweat; they’ll happen to some varying degree.

If you’re someone who cringes at the sight or smell of either, perhaps a deeper understanding of the science behind perspiration will ease your mind. So here are some fast facts that’ll help you better understand how both sweat and body odor work.

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There Are Two Types of Sweat

According to Chris Putman, senior deodorant designer for Secret deodorant, sweat is caused by heat and activity and stress. What differentiates them is their origin.

Sweat from heat and activity comes from the eccrine sweat glands. These are made up mostly of water and a small amount of electrolytes and protein. On the other hand, stress sweat—which causes the worst body odor of all three—activates the eccrine gland, in addition to the apocrine gland. The latter gets triggered via the bloodstream from adrenaline.

“The apocrine glands are larger and are concentrated in the underarms. They release a milky-looking substance that contains cholesterol, lipids, and proteins, which means much more nutrients for the bacteria living on our skin. The bacteria eat these nutrients, and this is what results in more odor,” says Putman.

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BO Is Actually Due to Bacteria

Body odor is made up of three components: bacteria, water, and food, such as proteins, amino acids, and oils from sweat and skin.

“Bacteria, in the presence of water, eat the food or nutrients and produce small molecules that we can smell as body odor,” says Putman.

Shaved Underarms Smell Less

Whether someone shaves their underarms or not is a matter of personal preference. One isn’t “better” than the other. However, keeping your pits shaved does reduce odor, since additional bacteria can accumulate on hair follicles.

The obvious way to ward off BO is by showering regularly with soap and water and wearing clean clothes. To control body odor between showers, use a deodorant or antiperspirant.

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Deodorant and Antiperspirant Aren’t the Same Thing

Speaking of those two, one of the biggest misconceptions is that they are one in the same. Au contraire, a huge difference lies between the two.

“Deodorants help control odor primarily by reducing our nose’s ability to smell it, by masking that odor with scent. They also reduce the amount of bacteria in the area, which is a cause of body odor,” says Putman. “Antiperspirants go one step further to not only kill bacteria and mask odor with fragrance but to form ‘temporary plugs’ that reduce the flow of sweat to the skin—what we call wetness.”

Nighttime Application Is Best

Deodorant or antiperspirant should be used daily, but according to Putman, one of the best ways to help protect against sweat is to prepare ahead of time and apply your antiperspirant at night.

“Nighttime application is most effective because your body is usually at a lower temperature and sweating more slowly so your antiperspirant can form a strong barrier against perspiration. If you want even more protection, you can apply again in the morning for additional security.”