Challenging the scalp with 'dry' wash shampooing (DW) on Chinese men: an in vivo study

Cosmetic habits show a strong diversity worldwide. The same applies to procedures that are considered as basic hygiene acts such as shampooing. Apart from common traditional shampoo routine, a special shampoo procedure, 'dry' wash is daily performed in Chinese hair salons. Without pre-wetting step, hairdresser applies the shampoo directly to dry hair with small quantity of water to create foam. Hand massaging is then offered on the scalp. This shampooing process is distinguished from traditional 'regular wash' by slightly diluted shampoo, and longer contact with the scalp and scalp massaging, all of which could be possibly considered as challenges to the structure and barrier function of the scalp. In this study, the effects of 'dry' wash on Chinese scalp have been investigated, in vivo, using regular wash as a control. A total of 67 Chinese males in two cohorts, non-dandruff and with dandruff, were included. In each cohort, volunteers were split into two groups, one with 'dry' wash and the other one with regular wash. Both shampoo methods were performed daily for five consecutive days using the same shampoo formulation. Volunteers' self assessment, clinical assessment by an expert and instrumental measurements were carried out. The results showed that Chinese 'dry' wash did not induce any negative consequence on the scalp physiology under such experimental conditions.