To put it simply: "Cell turnover is the continuous process of shedding dead skin cells and subsequently replacing them with younger cells," says board-certified dermatologist and Curology founder David Lortscher, MD.
This process is the "holy grail of healthy skin," as Rhea Souhleris Grous, Aesthetics Director at Union Square Laser Dermatology puts it, because the process makes skin look shinier and tighter, and gets rid of fine lines and wrinkles more quickly. "If you don’t cellular turnover, you have a buildup, and it’s like a traffic jam at the surface," says Grous. That stagnation can lead to issues such as acne, hyperpigmentation, milia, and uneven texture.
In order to understand why this cell turnover is critical to dealing with these issues—and to overall skin health, in general—let's kick it back to high-school biology and break things down a bit further. Every cell in your body has a life cycle, and in the case of adult skin cells, that cycle lasts around 28 days. (It slows down when you get older, but more on that later). New skin cells are born in the deepest layer of your dermis, called the basal layer. As they mature, they move through the epidermis toward the skin's surface. At some point during this process, they lose their nuclei, which means they're no longer active, living cells. "They become a thickened layer of dead cells, and over time, they slough off," says board-certified dermatologist Jason Miller, MD.
When these old cells fall off, the new ones rise to the surface to take their place. "As the top guy at the surface dies off, it makes space for the plump guy at the bottom to say 'my turn,' and replace him at the top," says Grous. And when those plump baby skin cells gets to the top, it's goodbye to dull skin and hello to a healthy, radiant complexion.
While your skin can handle the cell turnover process just fine on its own–eventually, the new skin cells will push up on their own and the old ones will fall off—there are certain things you can do to make it happen more quickly. This is where exfoliation comes in. "Your skin is going to to through cell turnover whether you exfoliate or not, but what ends up happening is the cells are detached from the skin and start to pile up on top of each other," says Rachel Liverman, CEO and co-founder of skin-care center Glowbar. "But unlike a snake shedding its skin, we don't just crawl out and leave a big long peel behind."
You can help your skin "shed" more quickly with either with chemical or mechanical exfoliants, which get the job done in different ways. "If you disturb the process, cellular turnover gets encouraged," says Liverman. Chemical exfoliants such as glycolic acid interact with the bonds between the dead cells and the skin, which helps loosen the cells and encourges them to fall off. Mechanical exfoliants (think: scrubs) rub the top layer of skin hard enough to physically remove the dead skin cells. In both cases, those dewy new cells will come out on top.
The real gold-standard ingredient for cell turnover, though, is retinol. "Retinol puts the whole process on fast-forward," says Dr. Miller. "It makes the progression of the cells through the skin and the sloughing of the top layer happen a little bit faster." As mentioned, cell turnover slows down as you get older, "which contributes to visible changes that we see in aging skin," says Dr. Lortscher. This, it's worth noting, is why so many derms recommend adding a retinol to your routine by the time you hit your late 20s.
And aging isn't all they can help with. Retinol (and retinoids, their Rx counterparts) is highly recommended for acneic skin, because a lot of what's clogging pores—and creating pimples—are those dead skin cells hanging out on the on the surface of your skin. "When you make cell turnover happen a little faster, it opens those pores," says Dr. Miller.
To add some retinol into your own routine, try everyone's favorite drugstore diamond, Differin ($13), or one of our other go-to product picks. If you've got sensitive skin, plant-based bakuchiol—like Herbivore Bakuchiol Natural Retinol Alternative Serum ($54)—is a great gentle alternative, as is Mara Primrose and Green Tea Retinol Oil ($120).
The best thing to keep in mind about cell turnover, though? Since your cells are shifting every 28(ish) days, it means that fresh, healthy skin is always right beneath the surface.
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