Avoid washing your hair every day and adapt the washing frequency to your hair type to preserve natural oils, prevent dryness, avoid a compensatory overproduction of sebum, and protect the hair fiber.

noli's read

The idea of adapting washing frequency based on hair type is scientifically valid, as highlighted by a review from the team of researcher d'Andrade in the journal Cosmetics (expert opinion). It is proven that washing too frequently with harsh surfactants removes protective sebum and alters the cuticle, a fact documented by a study by the team of Dr. Sinclair in the International Journal of Trichology (observational study). Furthermore, repeated exposure to water temporarily weakens the hair structure, increasing the risk of breakage during styling. However, the idea of a 'compensatory' or reflexive production of sebum following frequent washing is a popular belief that remains unproven. Research on skin physiology, particularly that published by Dr. Elsaie in the Journal of Cosmetic Dermatology (literature review), indicates that sebum production is regulated by hormones and genetics, not by a signal of surface dryness. Thus, daily washing may be perfectly suitable for very active scalps if performed with gentle formulas.

the sources

No named source held this one up — that absence is part of the verdict.