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Turns out, Grandma was right about going to sleep with wet hair.

If you’ve been air-drying your hair in hopes of effortlessly drip drying your way to healthier strands, you might want to sit down for the news we’re about to drop. According to UK-based Grazia magazine, an interesting study claims that air-drying is more harmful than blow-drying, and the reason is something we would never have suspected.

It seems the culprit is the length of time hair shafts remain wet. The longer hair stays wet, the more stress and damage is caused to strands. Before we get too far, towel drying is not the answer either. We’ve long known that towel friction isn’t the best for achieving smooth, lustrous locks, but this same study also concluded it might be more harmful than just holding the title of instigator of frizz—citing friction as a “major damage factor.” If you ask us, that doesn’t sound too promising.

As you might think, blow-dryer heat does cause more surface damage than the alternative, but air-drying caused cell membrane damage (i.e. more substantial and long-lasting damage). It turns out, our hair surface does a pretty good job of protecting and preventing deeper strand damage. We now finally have an answer to the age-old question: Does blow-drying damage hair? The key takeaway was to blow-dry with a continuous motion 15 cm (5.9 in) from hair in order to produce the smallest amount of damage. The closer to the hair you hold the blow-dryer, not surprisingly, the more heat damage is caused.

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Now, all this to say, it’s still too early to hypothesize whether we’ll take these scientific findings to heart come summer. Give up air-drying styles that show off our natural hair? Those odds aren’t looking good.