What pH tells you about a product
Your scalp's natural pH sits around 5.5. Products that fall far outside this range can disrupt the scalp's barrier and roughen the hair cuticle. Knowing this helps you interpret products more critically.
The pH scale runs from 0 (most acidic) to 14 (most alkaline). Healthy hair and scalp have an acid mantle with a pH of around 4.5 to 5.5. This acidity keeps the cuticle closed, the scalp balanced, and the hair resistant to bacterial growth.
Alkaline products, including many traditional soaps and some clarifying shampoos, can temporarily raise the hair's pH, opening the cuticle and causing frizz, tangling, and increased porosity over time.
Most conditioners are formulated at a slightly lower pH to help close the cuticle after shampooing. Ingredients like citric acid are often used as pH adjusters to bring a product into the right range.
Relaxers and permanent colour treatments operate at high pH levels by design; they need to open the cuticle to penetrate the cortex. This is why these treatments require particularly careful aftercare.