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Media Platforms Design Team

Let's start with the basics. Detergents and soaps—the cleansing agents in most shampoos—are great at lifting oil and dirt off the scalp and strands. The problem is, they're maybe a little too good at their jobs. Harsh ones can open up the cuticle and strip out the natural moisture in the hair shaft, leaving strands damaged and parched. That's where regular conditioners come in, smoothing down lifted cuticles and infusing dry strands with moisture. The idea with a co-wash is that it forgoes the first step, shielding strands from the damage of shampooing altogether.

So how, exactly, does the hair get cleaned? In the case of Purely Perfect Cleansing Creme ($40, purelyperfect.com), botanical oils like peppermint and sunflower loosen dirt and cause it to slip away. There are still some detergents in Pantene Truly Natural Co-Wash Cleansing Conditioner ($5, pantene.com), but there's also conditioning agents and natural oils to soften the blow. Wen Cleansing Conditioner ($32, sephora.com) moisturizes with glycerin and freshens strands with chamomile and rosemary extracts. Of course, here's one more reason—and it might be the most significant—co-washes are more gentle on the hair. Because they don't lather, they don't cause the hair to tangle and tear. Less tangling equals less breakage. Meaning for a similar result, you could try a sulfate-free shampoo, and vow not to swirl your hair into a knot when you wash it.

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Media Platforms Design Team

Here's who can get away with using these formulas: Women with very coarse or curly hair who have to be careful about shampooing anyway. Here's who can't: Those of us with fine hair, or women who get greasy hair after one day without a shower. Or at least that's what we thought until we tried it. Our tester has fine hair, but lots of it, and was sick of it getting greasy after just one day without showering. A hairstylist recommended a co-wash to balance the oil production on her scalp, which was spiking after using shampoos. And guess what? It worked. After a month, "my scalp is much less greasy," she reported. "Plus, because my hair isn't dry anymore, the knots and tangles I've always gotten are totally gone ." On the other hand, "it's always kind of dirty." Which is not to say it looks or smells bad. In fact, quite the opposite, it's just never puffy or squeaky clean. Bottom line: Pick your battles.

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Hannah Morrill
Contributor
Hannah Morrill is a writer and editor based in Portland, Maine. She’s an avid reader, an indifferent face-washer and a sunscreen/retinol evangelist.