Considerations for hair washing frequency
Q. How often should someone shampoo to maintain healthy hair?
This is the second most difficult question to answer in dermatology behind how often should I wash my face. I am not sure that all dermatologists would agree on the frequency of hair washing, and perhaps this is due to the fact that shampoo is to wash the scalp and beautify the hair. Hair does not really need to be washed. It is nonliving and does not produce sebum or sweat. It is the scalp that produces these materials that are then wicked from the scalp down the hair. Certainly, if the hair gets full of environmental dirt or food, it needs to be washed, but this is rare in adults.
The frequency of hair washing depends on the sebum and sweat production of the individual and the geometry of the hair. Hair that is straight will rapidly wick the sebum and sweat from the scalp while tightly kinked hair wicks very poorly. For this reason, individuals with very straight hair usually prefer to shampoo daily while individuals with kinky hair shampoo once every one to two weeks. It is likely that most Americans shampoo their hair too much, accounting for the huge sale of hair conditioners designed to replace sebum with a more cosmetically acceptable synthetic ingredient.
I think some excellent advice to give to patients is that shampoo should be applied to the scalp first and massaged to remove skin scale, lipids, and water-soluble dirt. As the shampoo is rinsed, it should be massaged through the hair. This allows the conditioning shampoo to cleanse during the phase when the shampoo concentration is high and the water concentration low. During the rinse phase, when the shampoo concentration is low and the water concentration high, conditioning will occur beautifying the hair shaft. This allows optimal hair appearance while encouraging proper scalp hygiene.