In July 2014 researchers from Brazil published their review of the medical scientific literature as well as their analysis of 123 international brands of shampoo to assess the effect of a low pH shampoo on the hair. All pH values of the shampoos analysed ranged from 3.5 to 9.0, with all children’s shampoos having a pH of over 5.5 (an acidic shampoo has a pH of under 7, an alkaline shampoo a pH of over 7). Results showed that a shampoo with a pH of over 7 appeared to increase friction between the individual hairs which could lead to cuticle damage and hair breakage. A lower pH shampoo also appeared to cause less frizzing. Interestingly, 75% of the salons shampoos but only 38% of the international brand shampoos had a pH of less than or equal to 5.0. The researchers believe that the pH value of the shampoo should appear on the label, but studies are needed to establish the best pH range for both scalp and hair health.
Gavazzoni Dias MF et al. The Shampoo pH can Affect the Hair: Myth or Reality? Int J Trichology. 2014 Jul;6(3):95-9