If you look at the directions on the back of a shampoo bottle, you’ll often be instructed to “lather, rinse and repeat.” At many hair salons, stylists will ask you if you want a second wash. But, not everyone agrees that you need to shampoo your hair twice. Here, experts share what they think about this debated hair-care ritual, and we take a look at what the science says too.
Featured Experts:
- Anabel Kingsley, a trichologist and president of Philip Kingsley, based in London
- Michelle Wong, PhD, a cosmetic chemist based in Australia
- Nicole Vincent, a hairstylist based in Las Vegas
- Rachel Silva, a hairstylist at Xenia Claudeth Salon in Cedar Park, TX
When You Might Want to Shampoo Twice
Trichologist Anabel Kingsley, president of Philip Kingsley, likes to compare double cleansing your hair to double cleansing your face when you’re wearing makeup. “You cleanse your face once if you wear your everyday makeup. However, if you are going out and wearing more makeup than usual, you might double cleanse. Or, you might need a more effective cleanser to remove your makeup. The same applies to the hair and scalp.”
According to Kingsley, these are the circumstances when she tends to recommend a second cleanse to her clients. “If you have fine hair that gets very oily fast, a double shampoo often helps to ensure all oil buildup is cleansed away for weightless roots. Also, those with a flaky or itchy scalp can wash twice with their targeted shampoo,” she explains. “The first wash acts to lift and exfoliate, and the second helps to rinse away any remaining flakes and oil.” Another instance might be if you have done a pre-shampoo treatment or used heavy styling products that create buildup. “You may want to wash twice to ensure that the product is completely washed—not just rinsed—away, so that no heavy residue is left on your strands,” Kingsley adds.
There are also other products, like clarifying shampoos and treatments, that are meant to provide a deeper cleanse. “For example, our Vitamin C Jelly Detoxifying Hair and Scalp Treatment ($44) is 38 percent more effective at removing more product buildup,” says Kingsley. “It’s also 31 percent more effective at removing more hard water mineral buildup, and 11 percent more effective at removing pollution than shampoo alone.” Many of these treatments are meant to be used once a week, or as needed.
What the Science Says About Washing Your Hair Twice
“I have a PhD in supramolecular chemistry, so this is my area,” says Dr. Michelle Wong, a cosmetic chemist. “There is nothing in the science that says that one wash with surfactants can’t get all of the oil and dirt off. In terms of chemistry, it is the same as when you’re washing dishes. Dishes don’t necessarily need to be washed twice. It depends on how dirty the plate is, your technique and the product you’re using. If it just isn’t very good at cleaning, or you just didn’t use enough, you might need to wash it twice. It even depends on things like the temperature of the water. You might find that your hair and scalp are happier if you do wash twice, but most shampoos are designed to wash well with just the one wash.”
What Hairstylists Think About the Double Shampoo
Rachel Silva, a hairstylist based in Cedar Park, TX, says, “In my experience, most clients need a double shampoo. Not all of them, but many do, especially those with denser or coarser hair. Or, clients who go several days between washings. I’ve used the same techniques for shampooing, and for many clients, one wash just isn’t enough. I can smell and feel the difference when I blow-dry and style. If my first shampoo doesn’t produce enough lather, then I hit it with a second. There’s always a difference between the two.”
Hairstylist Nicole Vincent (you may know her as “Nicole the Stylist” on TikTok) says that if she could give one tip that will help get everyone’s hair to a healthier state, it would be to shampoo twice. “It’s the easiest thing to follow. I don’t know why more people don’t do it. It’s literally right on the instructions: Lather, rinse, repeat. That is going to get all the extra dirt out of your hair. It will get you a better wash and you can go longer between your shampoo days. You’ll notice, too, that you’ll end up using less product, because the second lather will lather really, really well with just a dime-size amount. It will make a huge difference.”
The Bottom Line
Ultimately, despite what the science and stylists say, you know what is best for your hair. If you just ran a marathon and are drenched in sweat, your hair might benefit from a double cleanse. If you haven’t washed your hair in days and you’ve used about half a can of dry shampoo, washing twice could make a difference. However, none of this necessary, and many times, as Dr. Wong points out, a single wash is perfectly sufficient.