Why Does Your Sweat Sometimes, You Know, Stink?

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So there I was in the one hot yoga class I’ve ever been talked into taking, unsuccessfully attempting to hold Plank with wet palms and drippy feet while cursing all the life choices that had led me to that moment of feeling like I was in the second circle of hell. That’s when I started to smell the growing musk of a nearby practitioner. Particularly sensitive to smells, especially when hot and exhausted, I set my intention to not gag and maybe even prayed a little for death.

I thought I was alone in my misery until I caught another classmate complaining to her friend by the lockers after class. “I’m all for body autonomy…except when it comes to not wearing deodorant at hot yoga,” she said. “That should be against the law.”

I silently concurred while also thinking it was the most @OverheardLA-worthy comment I’d been privy to in recent weeks.

It also made me contemplate sweat itself. Why do some people perspire more than others? Why is some of it stinky and some of it benign? Should we be wearing deodorant while exercising? Was that other student correct in her theory that not applying it is a crime against humanity?

I moved on, probably to a snack because snacks are > pondering perspiration, until months later when I heard about a new deodorant purpose-made for staving off fitness funk. In an instant, I found myself back in that hot room tainted with the slight stench of au naturel human. Seemed like a sign to throw my (prayer) hands in the air, reopen the cold (sweat) case, and put together a perspiration primer.

So Why Does Sweat Stink?

Sweat itself “is generally odorless,” explains Marisa Garshick, MD, a dermatologist and assistant clinical professor at New York-Presbyterian/Weill Cornell Medical Center. It’s only partially responsible for the malodorous musk scientifically known as bromhidrosis. “Body odor results from the combination of sweat and the normal bacteria that live on our skin,” she says.

More specifically, “Odor is caused by the bacteria breaking down the components of sweat and producing that characteristic [BO] smell,” explains Navin Arora, MD, founder of Borealis Dermatology on Long Island.

But that’s not the only reason sweat can be…stinky.

          Not all sweat has the same propensity to be detected by smell. And yes, office-goers, you should beware. (Photo: Getty)

Different Kinds of Sweat Smell Different

As it turns out, not all perspiration is created equal—or even secreted by the same glands. There are three basic types of sweat:

1. Thermoregulatory Sweating
The most common type of perspiration, thermal or thermoregulatory sweating, occurs when the hypothalamus (aka the body’s thermostat) senses an increase in body temperature, such as during exercise or when standing outside in the heat. In response, the brain signals the sweat glands to get to work because sweating is the human body’s most effective cooling mechanism. Known as eccrine sweat, it’s produced by glands of the same name found throughout the body, which open directly onto the skin’s surface.

2. Psychological Sweating
Emotional or psychological sweating is triggered, as the name implies, by surges of intense feelings such as fear, anxiety, stress, embarrassment, excitement, or pain. Although this response to emotional stimuli begins when we’re wee babes, this kind of sweat typically doesn’t start stinking until the hormonal and physical changes associated with puberty occur. It tends to strike the groin, palms, armpits, soles of the feet, and face. This milkier sweat is produced by apocrine glands, which open into hair follicles which in turn provide sweat’s path to the skin’s surface.

3. Gustatory Sweating
The third kind of sweat, gustatory, will be familiar to regular viewers of Hot Ones on YouTube. It’s usually precipitated by eating or drinking something so spicy or hot that body temperature is elevated. In an attempt to cool itself, the body cues the aforementioned thermoregulatory waterworks.

That puddle of sweat left on yoga mats comes from a combination of the first two types, explains Arora. Workout-induced wetness is “primarily a watery, odorless sweat as a response to body temperature, primarily composed of water, salt, and electrolytes,” he says. This is mostly thermoregulatory or eccrine sweat.

Conversely, psychological or apocrine sweat occurs in areas with a higher concentration of hair follicles, such as the armpits, explains Arora. “Sweat produced by apocrine glands tends to be associated with stronger odor,” Arora says. “However, any sweat can lead to body odor if it interacts with bacteria on the skin.”

There are also differences in sweat rates and patterns that align with biology, says Arora. “Men generally have more eccrine glands, which produce a larger volume of sweat.” They also have higher testosterone levels, which lead to increased activity of apocrine glands, explains Arora. “Additionally, men often have more body hair, providing a larger surface area for bacteria to thrive.”

So yes, men may experience more issues with smelliness stemming from hormonal differences between the sexes, although it varies wildly based on the individual, says Garshick. She notes that bacteria breaking down the top layers of the skin can result in “an odor associated with the ingestion of onions or garlic.” Could that have been the cause of that unmistakable musk I couldn’t escape at class?

Man holding a stick of deodorant and reading the ingredient list while contemplating why does sweat stink? Read the ingredient list on deodorants with caution. (Photo: Getty)

Do Certain Deodorants Work for Certain Kinds of Stink?

Sherry Jhawar, co-founder of nez deodorant, thinks so. “I was always fascinated by the fact that all deodorants are ‘one size fits all.’ Everyone uses different products for different hair types and skin types but one deodorant has to do everything,” she explains.

That fascination led her to examine the different types of sweat and co-found a company that customizes deodorant formulas for different situations. She refers to it as “occasion-based deodorant.” According to Jhawar, the ingredients in Workout Sesh (zinc ricinoleate and bamboo powder) “address and absorb movement-induced eccrine sweat.” The ingredients in Board Meeting (bentonite clay) and Date Ready (charcoal powder) “address and absorb stress or excitement-induced apocrine sweat,” she explains.

But can certain ingredients in deodorant actually deter certain kinds of stink?

“Deodorants often contain antimicrobial agents that can reduce bacteria on the skin, addressing the smell associated with sweat,” Arora says. “Additionally, they can provide a psychological boost by making individuals feel more confident and comfortable during physical activities.”

His two cents about exercise-friendly ingredients is to “look for deodorants with antibacterial agents like triclosan or triclocarban that help control the growth of odor-causing bacteria. A pleasant fragrance can help mask odor [while] an alcohol base can keep the underarms dry.”

An added bonus of applying microbe-fighting deodorant, Garshick says, is “some of the same treatments we use to reduce bacteria in [regard to] body odor can also help to reduce [acne] breakouts and conditions like folliculitis.”

As with nail polish or shampoo, it’s wise to familiarize yourself with the ingredient list before you buy or use. Arora warns consumers to avoid parabens (“preservatives that can disrupt hormone function”), phthalates (“might interfere with the endocrine system”), propylene glycol (“can cause skin irritation”), and artificial colors and synthetic fragrances (if you experience sensitivity to either).

“Reactions can vary, so it’s important to find [a brand] that works well with your body chemistry and skin type,” Arora explains. Of course, even natural deodorants can contain ingredients and fragrances that lead to contact dermatitis, especially for those with sensitive skin—further proof that one size doesn’t fit all.

Wait, What About Anti-Perspirants?

Antiperspirants are designed to block the release of sweat. As such, they can also hinder, sometimes to a dangerous degree, the body’s ability to cool itself down.

Arora supports relying on deodorants over antiperspirants. “While [antiperspirants] can be effective in preventing body odor, it’s essential to allow some sweating during exercise to regulate body temperature,” he says. “Using deodorant, which masks odor but allows sweating, may be a better choice during workouts.”

He also notes that “finding a balance between managing bacteria and ensuring proper skin ventilation” is crucial for maintaining healthy skin. “The aluminum salt in an antiperspirant plugs up the sweat glands,” Garshick says. This can clog pores and lead to acne or other skin irritations.

And what about aluminum? For years, women, especially those who spent any time watching the news in the 1980s, have worried about suspected links between using antiperspirants or deodorant-antiperspirant combos containing aluminum and breast cancer. Older research suggested that aluminum could penetrate the skin and induce estrogen-like effects, which have been known to stimulate the growth of cancer cells. People also sounded the alarm about aluminum’s suspected link to Alzheimer’s.

More recent research has prompted both the National Cancer Institute and the Food and Drug Administration to say there’s no data to support those fears. “No conclusive evidence has been found surrounding aluminum’s potential association with Alzheimer’s or cancer,” Garshick says.

For those who are still leery, there are an astounding number of deodorant options on the market that are free of aluminum, including nez, Native, and Insta-famous Lume.

How Not to Stink When You Sweat

If you decide to roll on the deodorant, Arora also cautions you to pay attention to the amount you apply before you head to the gym or yoga studio. “A few swipes or a thin layer applied evenly should suffice. Applying too much can lead to product buildup, which might be uncomfortable and less effective,” says Arora.

So, yes, sweat happens, but serious stink doesn’t have to. With no downside, according to the derms, grab a stick and swipe those pits before heading to the studio so you can avoid being that person committing an olfactory offense during Savasana.

Photo Credits:
Row 1, from left: Nathan Dumlao | Unsplash; Jordi Salas | Getty; Avi Richards | Unsplash; Getty; Imgorthand | Getty

Row 2, from left: Richard Drury | Getty; Maskot | Getty; Constantinis | Getty; Logan Weaver | Unsplash; Freshsplash | Getty

Row 3, from left: gorodenkoff | Getty; Hiraman | Getty; skynesher | Getty; Thomas Barwick | Getty; Patrik Giardino | Getty


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