Many of you may have heard about the ‘no poo’ trend of not washing your hair with shampoo, especially with social media influencers touting its supposed benefits. You may be thinking of trying it yourself – but before you do, what does the science say about ‘no poo’?

How Washing Your Hair Affects Oil Production (Or Doesn’t)

Sebum, or what we often think of as oil, is secreted from the sebaceous glands that open into each hair follicle and then distributed onto the surface of the skin. ‘No shampoo’ converts believe that when you shampoo, you strip the hair of its natural oil and this causes the hair to overcompensate by producing more oil – so in other words, washing or not washing your hair controls how much sebum you produce. However, this is not how it actually works.

Sebum production is a constant, mostly determined by sex hormones; androgens like testosterone increase oiliness, while female hormones decrease oiliness. We all produce both types of sex hormones, but to varying degrees.

Not washing your hair doesn’t slow the production of sebum. The only situation where an external influence changes the hair’s outer lipid coating is when the hair is damaged by chemical treatments, causing disruption to the fat layer coating the cuticle.

The Scalp Microbiome

The environment on the scalp naturally has microbes, which we now refer to as the scalp microbiome. Just like the gut has bacteria, our scalps are also host to bacteria and fungi. Overgrowth of certain bacteria and fungi (Staphylococcus epidermidis, Malassezia globosa, Malassezia restricta) on the scalp leads to dandruff and scalp disorders. When you don’t wash your hair, dysbiosis (an imbalance of the microbes) more easily occurs. The malassezia fungi metabolize the triglycerides in sebum, resulting in an unsaturated lipid byproduct. The unsaturated lipids irritate the top layer of the skin, resulting in an inflammatory reaction, flaking and dandruff.  

Why Water or Conditioner Alone Don’t Work

I recommend that my patients aim to wash their hair every day, or at least every second day, to prevent the accumulation and breaking down of sebum. I often put it like this: if you wash your face and body every day, why would you treat your scalp any differently? It is also important to use shampoos and conditioners that have a similar pH to the skin’s pH – about 5 to 5.5. At this pH, the microorganisms on the skin’s surface are kept in check. It is especially important to wash hair post-exercise. Our scalps naturally sweat, but during exercise, you sweat even more. This creates a warm, humid environment where yeasts can flourish. 

Most dirt and sebum are not soluble in water and can’t be removed with water alone. That is why shampoos contain surfactants – compounds that cleanse the hair and scalp by acting as detergents and foaming agents. Using an appropriate shampoo therefore helps to maintain personal hygiene and reduces scalp inflammation, itching and odor – something water alone can’t do.  

If You Have a Flaky Scalp

If you have flakes or dandruff you will benefit most from a medicated shampoo, which has ingredients to kill off over-proliferating yeasts and bacteria on the scalp. Common ingredients used in medicated shampoos include, but are not limited to zinc pyrithione, octopirox, ketoconazole and selenium sulfide. If the scalp appears healthy, a non-medicated shampoo and regular hair washing will be enough to keep the yeasts at bay. 

So my verdict on the ‘no shampoo’ movement? I would not recommend it, as from what I’ve seen, it leads to scalp irritation, inflammation, scaling and odors.

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  1. So many people are oblivious to the fact that shampoos that grow your hair fast (of course with no sulfates, no parabens, no DEA) exist. Hair styling enthusiasts now may experience longer hair and achieve more options. Certainly worth considering.

    When you’re looking into alopecia, hair damage, avoiding skin disorders, fast hair growth, hair care generally, similar thoughts become relevant.

    For the most part, you will want to avoid hair products and treatments that include chemicals such as parabens, DEA and sulfates.

    What is healthy for your hair is beneficial for your skin as well.

    Clearly your content here is so useful for many reasons. It steers away from the usual pitfalls and errors most fall into- buying ineffective alternatives. Keep up the great content!

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