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Ultimately, whether you blow-dry your hair, let it air-dry or sleep with it wet is entirely down to personal preference, but from a dermatologist’s point of view, it’s best to dry hair thoroughly before going to bed. “Not just for better scalp health,” says Dr. Wong, “but also because your hair is at its weakest when wet and therefore most prone to breakage in this state.” Proudman agrees: “Wet hair can easily be broken, so I always advise to go to sleep with dry hair for both scalp and hair health.”