The Science of Butt Sweat

The Scenario: Your “friend” loves to dance. At late house parties, she’ll spin around with friends into the wee hours with a frozen pomegranate margarita in hand, beads of condensation dripping off the bottom of the cup in an overcrowded living room.

That cup isn’t the only thing sweating. During the party, you’ll see a patch of sweat spread on your friend’s rear, foreboding, slow but immediate like The Blob taking over a city in old horror movies. You’ve seen this happen while she’s Milly-Rocking on the makeshift dance floor, but also when she’s trying to do her own taxes or have a conversation with her mother on the phone. Whether it’s heavy activity or anxiety, your friend is wringing out her pants at the end of the evening.

What’s the deal? Why does my friend’s butt get sweatier than the rest of her body?

The Reality: Sweating is a normal and necessary function that regulates your body temperature; without it, your friend could overheat. But when two skin areas—such as underarms, palms, soles of the feet and butt cheeks—touch, rub, or fold together, the sweat can get a little intense. “The reasons why may be partially related to the density of sweat glands and the endocrine glands in those specific locations,” says Edith Bowers, associate professor in the dermatology at the University of North Carolina, who has a special interest in hyperhidrosis—also known as excessive sweating.

Whether your friend is tearing up a dance floor, feeling emotional (think, after several dances and several drinks) or having hormonal fluctuations, her nerves activate her sweat glands, and may hyperactivate them. This may result in a buttcrack sweat storm that makes them feel self-conscious. “Emotional stress can certainly trigger those same nervous system signals to increase sweating in those areas as well,” Bowers says.

The Worst That Can Happen: Your friend’s excessive ass-piration can leave more than salty stains on her pants; it can lead to a lot of embarrassment. She might even experience social anxiety, preventing her from doing activities she’d otherwise enjoy, Bowers tells me. Another nasty side effect: potentially developing skin conditions like fungal infections, itch around their groin area or skin in their butt area getting inflamed due to moisture, friction and/or lack of air circulation (medically called intertrigo). “Having chronic moisture, especially in the buttocks or groin area, probably predisposes you to other skin conditions as well,” Bowers says.

Excessive sweating can cause severe problems for your friend that requires a dermatologist’s attention, whether it’s for no apparent reason or due to an underlying medical condition that’s actually causing the sweating.

What’s Probably Happening: Most of the time, excessive sweating is harmless. Only about 2 to 3 percent of the population suffers from hyperhidrosis. Since much of this excessive sweating happens on your friend’s ample bottom half, it may be inescapable. “All of us sweat, and all of us sweat everywhere, including in our butts, most of us aren’t really bothered by it,” Bowers says. “But a not insignificant percentage of people experience such excessive sweating that it’s visible to other people and causes emotional stress, and those are the folks who might seek out treatment.”

What to Tell Your Friend: What can your friend do to keep that wagon she’s draggin’ cool and under control? Powders can absorb moisture, although you want to leave your clinical strength antiperspirant where it belongs: In your armpits. Prescription aluminum chloride is a salt solution used as an antiperspirant all the time, but can cause a rash, Bowers tells me. “It’s a tough area to use prescription antiperspirants; I’ve had some patients try it and the problem is it can be a little too irritating,” she adds. “That area is especially tough.”

Bowers does point to some systemic medications a derm will prescribe to your friend, but should only be used if their excessive sweating seems extreme since the meds may wring out the moisture in their body and put her in danger of overheating. Bowers has seen patients who were distressed enough about their excessive sweating to go this route, especially since it’s a difficult area to treat, but they have to be sure they stay cool and hydrated during workouts and strenuous exercise.

Your friend’s best bet is to stay as cool as possible—she should wear moisture-wicking fabrics and let her sweat evaporate. Otherwise, maybe just wear black and start adopting a minimally active two-step for the next party.

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