Everyone sweats, but why do some people perspire more than others? Why does some sweat stink? Should we all be wearing deodorant while exercising? Is not applying it a crime against humanity? I chatted with dermatologists to find out.

Why Does Sweat Stink?

Sweat itself is “generally odorless,” explains Dr. Marisa Garshick, 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 B.O. smell,” explains Navin Arora, a dermatologist based in Long Island, New York.

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

3 Types of Sweat

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 babies, 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.

Non-Stinky Sweat Versus Stinky Sweat

Workout-induced wetness is “primarily a watery, odorless sweat as a response to body temperature, primarily composed of water, salt, and electrolytes,” Arora says. This is the kind of sweat that manifests as a wet puddle left behind on gym equipment or yoga mat; it’s 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.”

Men Typically Sweat (and Smell) More Than Women

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.”

Do Certain Deodorants Work for 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.”

Deodorant Ingredients to Avoid

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.

Wait, What About Antiperspirants?

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.

Does Using Antiperspirants Cause Cancer?

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 American Cancer Society 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 Native and Lume.

How Much Deodorant Should You Put On?

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 gym studio so you can avoid being that person committing an olfactory offense during your bench press.

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