The "no-poo" movement encourages people to forgo traditional shampoos.

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How often should you wash your hair? A dermatologist debunks the “no-poo” movement

Is there any science behind the “no-poo” movement?

Getty/PhotoAlto/Frederic Cirou

If you’ve watched even one episode of Queer Eye, you’ve probably heard Jonathan Van Ness proclaim that people should not wash their hair daily. The famed hairstylist likens it to washing your favorite t-shirt every day; pretty soon, your brightly colored garment looks like it’s being sold as “vintage” at Urban Outfitters — faded, threadbare, and generally looking worse for wear.

In recent years, consumers have started paying closer attention to the ingredients in their shampoo; ones formulated without parabens or sulfates are far more ubiquitous than they were a decade ago. Even more recently, the so-called “no-poo” movement has gained traction — cleaning one’s hair without traditional shampoo.

But as someone who has extremely fine hair with a tendency to get oily quickly, the idea of forgoing shampoo altogether is somewhat terrifying. At the same time, I have a friend with very thick, curly hair who never uses shampoo — only conditioner. So how often should we wash our hair? And is there any science behind the “no-poo” movement?

How shampoo works

To understand the pros and cons of shampooing, we first have to understand what shampoo does. On our scalp, at the roots of our hair, are sebaceous glands. These secrete sebum, what we think of as oil. Sebum protects hair from drying out. Unfortunately, dirt and residue from hair styling products can cling to sebum, resulting in your hair feeling oily, weighed down, or generally icky.

The cleaning agents in shampoo are called surfactants. Each surfactant works slightly differently, but the gist is that all of them attract the oil, dirt, or sebum, displacing it from the hair and scalp and into the shampoo. Then, when you rinse the product off your locks, all that ick goes down the drain with your lather.

Dermatologist Jeffrey Hsu says, “If you are very active, sweat a lot, or have oily hair, the oil and sweat build-up can capture dirt. You need to be washing much more often than those that do not have such an active lifestyle or have very dry hair.”Getty

Unfortunately, surfactants aren’t necessarily discriminating. They can be a bit like antibiotics: They get rid of the grime, yes, but they also remove some oils that might still be beneficial to your hair. This is why many shampoos also contain some conditioning agents (and also why conditioner is so important to prevent hair breakage like split ends.)

How often should you wash your hair?

There’s no single recommendation that makes sense for all hair types, Jeffrey Hsu, a dermatologist in Illinois, tells Inverse. Because everyone has a different hair type, how long one should go in between washes will depend on their specific hair type and lifestyle.

“If you are very active, sweat a lot, or have oily hair, the oil and sweat build-up can capture dirt. You need to be washing much more often than those that do not have such an active lifestyle or have very dry hair,” Hsu says. “Likewise, someone with curly hair may tend to be on the drier end. And certainly, someone experiencing thinning hair or hair loss will need to wash their hair less often due to possible breakage from washing and sleeping with wet hair if they do.”

What happens if you wash your hair too much?

Remember early in the pandemic when the public health advice was to wash your hands “more often than you think you need to?” You may have ended up with dry, cracked hands from all that soapy lathering. If you’re washing your hair too much, the same thing can happen because it’s stripping the oils from the skin, which can cause dry, flaky hands (or scalp), Hsu says.

“However, like the skin on your face or body, the scalp is part of the skin as well. Everyone has different hair types: dry, oily, color-treated or thinning hair,” he says. “So the frequency of washing is highly dependent on hair type. Someone with oily hair can wash their hair daily while someone with thinning or dry hair should not.”

What’s the deal with the the “no-poo” movement

While the phrase “no-poo” may not immediately conjure hair care images, that is indeed what the movement is about. It simply means cleansing or treating your hair with something other than traditional shampoo. Some people who follow this method use baking soda, followed by apple cider vinegar.

“As in anything relating to skincare, pH levels are very important. Mixing a wash yourself, ingredients not only can potentially react to one another in unexpected ways, but you have no way of knowing the pH levels in what you are making,” dermatologist Jeffrey Hsu says. Getty/Michelle Arnold

It’s not, however, something Hsu advises.

“While some of these ingredients used are harmless and potentially beneficial for the health of the hair, as a dermatologist, I cannot advise doing any DIY treatments yourself,” he says. “As in anything relating to skincare, pH levels are very important. Mixing a wash yourself, ingredients not only can potentially react one another in unexpected ways, but you have no way of knowing the pH levels in what you are making.”

Companies have hopped on the no-poo trend, touting a new, shampoo-free era of hair care.

Hsu has concerns about those products as well. He says that there aren’t many studies evaluating if these companies hold up to their claims, “from a dermatologist standpoint, I do see a couple of issues here.”

The soap ingredients in shampoo are often needed to truly cleanse hair of dirt, sweat, and debris.

“Without proper or thorough cleansing, these build-ups can cause weakening of the hair follicles,” he says. “It seems like most of these no-poo shampoo replaces the soaping agent with baking soda. The problem with baking soda is that it strips the skin mantle, which is needed to protect the skin, in this case, the scalp. Over long-term use, it can lead to unnecessary scalp issues.”

So instead of going no-poo, it may be better to just go for...reduced-poo. Instead of forgoing shampoo altogether, you can try cutting back how much you use and how often and see if your hair becomes even more shiny and lustrous or turns uncomfortably oily. If it’s the latter, you may want to stick with your regular shampooing schedule.

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