pH (or hydrogen potential) is a measure that defines the acidity or alkalinity of a physical environment. It is measured on a scale from 0 to 14.
- A pH of 7 is equal to a neutral pH.
- A pH lower than 7 is acidic
- A pH higher than 7 is alkaline
The pH of the skin is one of the main protection of the skin. It is usually acidic and between 5 and 5.5. This is this acidity that protects the skin from pathogenic bacteria. The pH of the skin is constantly challenged by external aggressors such as pollution, temperature changes, and harsh products. This will lead to an imbalance in the pH of the skin and cause changes in the skin type and impaired barrier function.
Did you know? Most soaps are alkaline, which in the long run alters the protective symbiotic flora and the natural hydrolipidic film of the skin which can be dehydrated. At that moment, the skin becomes more sensitive to external aggressions like dermatosis such as allergies, irritations, eczema….
Therefore, it is essential to choose gentle soaps for the skin that respect its pH.
Hair and scalp both have an acidic pH. The average pH of the scalp is more or less like the one of the skin around 5.5 while the one of the hair is around 3.5 if healthy hair. The acidity comes from the hydrolipidic film which helps to maintain the hydration of the hair and protects it against chemical and physical aggression.
Did you know? Hair products can influence the pH of the hair. For instance, a product with alkaline pH, such as ammonia, will soften the cuticle and open the scalps to facilitate the penetration of pigments during coloring.
Products with an alkaline pH deeply damage the hair by removing its scales. As evidence of that hair becomes coarse, porous and brittle.
These products can also increase the hair’s negative electrical charge and therefore increase static electricity. On the contrary, a product with an acidic pH will tend to tighten the scales, smooth the hair and make it shiny.
Overall, to keep a healthy scalp and hair, it is recommended to use a sulfate-free shampoo with a pH of 5.5 followed by haircare containing cationic agents (conditioning agents) with a lower pH, to close scales and reduce static electricity and frizzy hair.