How many times per week should you wash your hair?

As a general rule, washing hair every day is often discouraged, but this recommendation is partly based on a misconception. In fact, our hair produces a lipid-based fluid, called sebum, which protects the scalp and hair from external aggressions. Shampoo is an emulsifying product that captures and removes excess oil, dirt, and buildup from hair products. When it is well formulated, it should not dry out or weaken the scalp.

Moreover, contrary to what is often claimed, frequent washing does not lead to an overproduction of sebum. This phenomenon is mainly observed when overly harsh shampoos disrupt the scalp, triggering reactive hyperseborrhea. Conversely, when using gentle, appropriate formulas and applying a conditioner to protect the hair fiber, frequent washing does not weaken the hair.

Therefore, there are no strict rules governing how often hair should be washed.

It depends more on factors such as your hair type, its texture, your lifestyle, and your environment. Thus, how often you wash your hair is above all a personal decision, based on your own comfort, sensations, and well-being. For example, some people with coily, dry, or very curly hair wash it once a week without any particular problems. This frequency is explained both by the naturally drier nature of this hair type and by practical constraints, since caring for it takes longer and often requires restyling after washing. At the same time, people with straight hair often prefer to wash it more frequently to avoid a flat and visibly oily appearance.

That said, if you do not wash your hair often enough, excess sebum, dirt, pollution particles, dust, and dead skin cells can accumulate, just as they do on the skin of the face. This can lead to itching, irritation, and visible flaking. A study has specifically examined the effects of infrequent washing on the scalp. The researchers observed that the amount of yeasts belonging to the genus Malassezia increased over time after the last shampoo. This microorganism feeds on sebum, which it converts into fatty acids that can trigger an inflammatory response, causing itching and redness. It is also involved in the development of dandruff and seborrheic dermatitis.

It was also observed that itch intensity increased significantly within 72 hours after shampooing, coinciding with the gradual accumulation of sebum and promoting the proliferation of Malassezia. Conversely, increasing the frequency of hair washing helped reduce flaking, redness, and itching, as well as the amount of Malassezia and the level of pro-inflammatory cytokines. The same study showed that daily hair washing did not damage the hair fiber and helped improve scalp comfort.

Ultimately, there is no universal washing frequency. If your hair is visibly oily, if your scalp feels itchy or shows flaking, these are signs that it is time to wash it. Conversely, if your scalp feels comfortable, without a greasy sensation or discomfort, there is no need to increase how often you wash it. The key factor remains choosing products that are suited to your scalp, so you can cleanse it effectively without disrupting its balance.

• DRAELOS Z. Considerations for hair washing frequency. Dermatology Times (2014).

• PUNYANI S. & al. The impact of shampoo wash frequency on scalp and hair conditions. Skin Appendage Disorders (2021).