What good is a chiseled physique if it's covered in blackheads and puss-spewing pimples? Oh, and don't forget those huge cysts that feel like face-eating tumors.

Unfortunately, a lot of guys' faces, backs, and chests revert to puberty when they man up in the gym, says Jeremy S. Fenton, M.D., a board-certified dermatologist with the Schweiger Dermatology Group in New York City. But, while breaking a sweat is linked with acne, it's not sweat that's actually causing it. It's how you deal with it, Fenton says.

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That's because your pores are entirely different than your sweat glands, which can be split up into apocrine and eccrine glands. The first are mainly found around your armpits and junk, and are responsible for both sweat and foul smells. The latter are virtually everywhere, and they exist to cool your skin and keep you from overheating. They spit out water and salt, and are to blame for anything that drips into your eye mid-workout.

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All that sweat, on its own, doesn't cause acne. However, sweat is meant to evaporate quickly (which removes heat from your skin and helps you cool down). But, when you trap it between your skin and clothes, it can't do its job. Instead, all that moisture seeps into your pores, mixes with the cocktail of bacteria, fungi, and mites that already hang out there, and produce a pimple. Hence why you may get more back-ne when you're sporting compression shirts or—and we shutter to picture it—butt-ne when you're squeezed into bicycle shorts.

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But, if you try to unsoak yourself with a wipe with the hand or scrub with a towel, you could end up making things worse. "In addition to spreading bacteria, the friction can irritate the skin and disrupt the surface, which can clog the pores with dead skin cells and lead to inflammation," Fenton says.

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What's more, if you're really hitting it hard in the weight room, you also could be triggering your skin's non-sweat glands, called your sebaceous glands, to release pimple-producing oil and stop up your pores, he says. That's because your sebaceous glands are largely controlled via hormones (hence why your ninth grade school picture looked so awful), and when you pump iron, you pump up your levels of testosterone, he says. While that's great for your muscle-building capacity, it's not so great for your skin.

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So, to get your sweat on without turning your skin into a cesspool, Fenton recommends working out in breathable, wicking gear and and washing immediately following your cool-down. Opt for a gentle cleanser and resist the urge to scrub. It would also be in your best interest to follow these tips on how to fight adult acne like a man.

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