How frequently should one shampoo? 

There is a lot of talk at the moment about not washing your hair.  Social media ‘influencers’ have been touting the supposed benefits of not washing your hair. But the science says differently.

Sebum, or what we often think of as oil, is secreted from the sebaceous glands. A sebaceous gland opens into each hair follicle. This sebum is then distributed onto the surface of the skin.  Hairs and sebaceous glands are all over the body, with the exception of the palms of the hands, and soles and dorsum of the feet. Converts of the ‘no-shampoo movement’ say that when you shampoo, you strip the hair of its natural oil and then the hair overcompensates. This implies that washing or not washing your hair controls sebum production. This is not the case. Sebum production is a constant. It is predominantly under the control of the sex hormones; androgens, like testosterone, increase oiliness where female hormones decrease oiliness. Not washing your hair isn’t going to slow the production of sebum. The only situation where the lipids coating the hair can be changed by an external influence is if the hair is damaged by chemical treatments, as this can damage the fat layer coating the cuticle of the hair. 

The environment on the scalp naturally has microbes. We now refer to it as the scalp microbiome. Just like the gut has bacteria within it, our scalps are hosts to bacteria and fungi too.  Overgrowth of certain bacteria and fungi of the scalp (Staphylococcus Epidermidis, Malassezia Globosa, Malassezia Restricta) is correlated to dandruff and scalp disorders. When you don’t wash your hair, disbiosis and overgrowth of these microbes more easily occurs. The Malassezia fungi metabolise triglycerides in sebum, resulting in an unsaturated lipid by-product. The unsaturated lipids irritate the epidermis, resulting in an inflammatory reaction and flaking; dandruff is often the result.  

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; I wash my face and body every day – why would my scalp be any different? 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. Most dirt and sebum are not soluble in water and can’t be removed with water alone. Therefore, a shampoo containing surfactants is needed. Surfactants are compounds that cleanse the hair and scalp by acting as detergents and foaming agents. Using an appropriate shampoo will help to maintain personal hygiene, and reduce scalp inflammation, itching and odour.  

It is especially important to wash hair post-exercise. Our scalps naturally sweat, but during exercise, this response is heightened. This creates a warm, humid environment where yeasts can flourish.  

If a patient already has flakes/dandruff, they will benefit most from a medicated shampoo, which has the ingredients to kill off the over-colonised yeasts and bacteria on their 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. 

What about sulphate-free shampoos? They reduce the chances of irritation but it must be said that the chance of irritation from a sulphate-based shampoo is very low anyway. 

As for the ‘No-Shampoo’ movement? I have had patients where this has led to irritation, inflammation scaling and scalp odours; I would not recommend it.

Chelcey Salinger IAT

Member, International Association of Trichologists