7 Science-Backed Hair-Washing Rules to Live By

If you’ve read a beauty headline lately, you’ve probably heard of the no-poo trend. And the cleansing conditioner movement. And maybe even reverse shampooing.

But wait, you may have thought — quite sanely — what’s wrong with the good old lather-rinse-repeat?

Of course, different hair-washing routines work for different women, and there’s no one-size-fits-all answer. But, we wondered, what does science have to say? We turned to cosmetic chemist Randy Schueller, host of the excellent Beauty Brains podcast, for a trend-averse, evidence-obsessed skeptic’s top washing and rinsing tips.

  1. Condition, condition, condition.
    If you’re after smooth, shiny hair, conditioner is the most important element of the shower routine, Schueller says. Conditioners contain polymers, such as silicones, that leave a covering on the hair even after it’s rinsed. This residue helps to smooth the cuticle, increasing shine and reducing roughness. It also decreases the amount of friction between your strands, making your hair more silky. “Just doing a good job on the conditioning piece will overwhelm problems with your water and a lot of other issues,” says Schueller.
  2. High-end products aren’t necessarily better.
    Whether you buy them at the drugstore or your salon, all shampoos and conditioners will deliver clean hair. While Schueller says that high-end products do generally perform better, it isn't true across the board—and marketing and packaging, not the ingredient quality, are typically the reason for the mark up. But that doesn’t mean you should feel bad about splurging on products you love, he says: “If you like the way they smell and feel in your hair, there’s no reason you shouldn’t buy them."
  3. “Natural” doesn’t always trump synthetic.
    We often assume that “natural” products are good and “synthetic” formulas are bad. But that’s a broad generalization that stems from misconception, Schueller says. While conditioners and shampoos will advertise natural ingredients, like avocado or jojoba oil, on the bottle, those are mainly just marketing gimmicks, he says. “Those things are almost always added just to make the product look a little more enticing,” he explains. “You have to look past the manufacturer hype and find what really works for your hair.”
  4. Skip the cold water rinse.
    You’ve undoubtedly heard that finishing a shower with cold water can seal your cuticle and make your hair shiny. But save yourself the shivering, says Schueller—while sealing the cuticle does restore shine, that comes from conditioning. “Just reducing the temperature won’t cement the cuticle back down again,” says Schueller.
  5. The way you dry your hair matters more than your shampoo.
    Hands down, the biggest cause of hair damage is simply washing and drying it over time, Schueller says. “Every time you wash and dry your hair, the hair fiber swells up. The outer layer, which is the cuticle, can’t really expand, and so the cuticles sort of pop up a little bit. Then, on top of that, people will towel-dry their hair very vigorously to get it dry—and that friction is horrible for hair,” he explains. Using an absorbent towel reduces two of the most major sources of damage, he says: the friction from towel-drying and the heat from blow-drying.
  6. Embrace dry shampoo.
    When it comes to hair health, “anything you can do in the care of not over-washing your hair and being more gentle when you dry your hair, that’s probably the biggest fix,” says Schueller. Which is why he’s a big fan of using dry shampoo to extend the time between washings. In fact, while every hair type—dry, oily, long, short, colored, virgin—has different needs, he says, dry shampoo is one of the few universally good-for-hair products.
  7. Find your own way.
    So should you start co-washing, stop shampooing, or overhaul your product routine? The answer, Schueller says, ultimately depends on you and your hair type. For some, going “no-poo” may leave your hair a greasy mess. “But for some women, depending on the length of hair and how oily your scalp is, you may be fine shampooing much less frequently,” he says.

And the same goes for ingredients. Silicones might be too heavy for very fine or curly hair, for example, but work wonders on thicker strands. And while sulfates are safe and effective cleansers, you may want to avoid them if you have sensitive skin. “It all depends on your personal preference,” Schueller says. “What’s good for one person isn’t necessarily good for another.”