When I opted last year to try a month's worth of infrared sauna sessions, the thought occurred to me just after a handful of treatments: What the hell was going on with my skin? I mean this in only the positive sense—somehow, lying in a pool of my own sweat for an hour twice a week had magically given way to a clear, dewy glow. And even though a better complexion had already been relayed to me as one of the benefits of the infrared sauna, it was no less miraculous to me that I could experience such a beautiful side effect of something so undeniably gross.
But it's also kind of the anomaly of working out, right? While we're instructed (and rightfully so) to cleanse any residual grime from our faces after breaking a sweat to avoid any breakouts, our skin looks undeniably better when we exercise consistently. So is it the act of sweating in and of itself that leads to a bright, younger-looking complexion, or is it something else? To find out, we deferred to dermatologist Whitney Bowe—and it turns out there's some really fascinating science behind this phenomenon. (Spoiler: Fitness really is the fountain of youth.)
You're not just toning up your muscles.
"We often think about the benefits of exercise in terms of fitness and weight control, but we don't usually think of its key role in keeping skin looking young and firm," says Bowe. In reality, exercise is actually one of the most potent anti-aging treatments out there—no overpriced skin creams necessary. "Surprising new research shows that exercise not only does keep your skin healthier, but it can actually reverse skin aging in people who begin an exercise regimen even later in life! Really a game changer."
The science behind this comes down to variations in the different layers of our skin. "As we age, we want certain layers of our skin to stay thin, and we want other layers of our skin to stay thick," explains Bowe. "The natural aging process of skin entails a gradual thickening of the outermost layer of our skin, the stratum corneum." Once we reach a certain age—usually around 40, says Bowe—that outer layer begins to get denser, drier, and flakier. Meanwhile, the deeper layers of our skin get thinner and less elastic and start to ripple—which translates to the outermost layer as wrinkles and sagging skin. It doesn't help that environmental stressors like pollution and sun damage only speed this process along.
But the study Bowe cites proved that exercise actually reverses this process on a cellular level. "Exercise can impact the number and health of the mitochondria in our skin cells, and thereby can make them behave as though they are younger (translation: more collagen, improved hydration, less sagging)." (If you're curious about more of the specifics on this topic, Bowe covers it all in her book The Beauty of Dirty Skin, $15).
Sweating is good for your skin… with some caveats.
Namely that washing your face ASAP after working out is a very good idea. But sweat actually serves much more of a purpose than just keeping you cool. "Sweat contains natural alternatives to antibiotics called antimicrobial peptides," says Bowe. "The specific antimicrobial peptide in sweat, dermcidin, is pumped onto the skin via the sweat glands and coats the skin, thereby providing protection against infection from other microbes and harmful germs."
As cool as this process is, it's important not to wait it out. "If sweat sits on the skin too long, it can irritate the skin," says Bowe. "Specifically, the ammonia and urea in sweat can cause irritation and inflammation if left on skin too long. The sodium in sweat can dehydrate skin if left too long on the surface, and the evaporation of sweat from skin can aggravate people prone to eczema."
It's also important to note that the idea of "sweating out toxins" is largely a myth. While we do sweat out trace levels of metals and BPA, scientists have found that it's not enough to markedly improve our health; the bulk of that task is up to the kidneys and liver instead of our sweat glands.
Which brings me back to my experience in the infrared sauna: The real reason my skin looked so great probably had more to do with the fact that heating my body from the inside out increased my heart rate and circulation, effectively putting my body through a cardio workout every session. "As we continue to exercise and our body temperature rises, vasodilation occurs, which means that our blood vessels dilate or become wider," explains Bowe. "This increases the flow of blood to the skin. Over the long term, this causes positive changes to the vasculature that supports the skin and keeps the skin young and healthy." (It's also why giving your skin a temporary glow can be as simple as flipping upside down.)
Don't scrub your skin after a workout.
Less is definitely more if you want to avoid acne and inflammation—and that goes for cleansing, too. "I recommend that my patients either work out with clean, fresh skin, or with breathable, lightweight, and/or oil-free products that are less likely to clog your pores, which can result in breakouts," says Bowe.
After your sweat sesh, cleanse—but gently. "You don't need to scrub your face clean after a workout," says Bowe. "Instead, wash using a gentle, pH-balanced cleanser, and pat dry." She recommends the La Roche-Posay cleanser shown above.