pH measures how acidic or alkaline a substance (usually a liquid) is. Healthy hair and skin both have a pH ranging from 4.0 to 5.5 (this is acidic).
This film of acid that covers skin is called the acid mantle; it acts as a barrier to undesirable toxins, viruses and bacteria that try to enter the body. As most of these contaminants are alkaline they are neutralised by the body's acid mantle. Put simply, the scalp's acidity protects it from infection.
What is the pH of shampoos?
Shampoos are normally mildly acidic with a pH of 4 to 6.
What is the pH of conditioners?
Conditioners are normally more acidic than shampoos with a pH of 3.5 to 5.0.
Is the decrease in pH as we move from shampoo to conditioner intentional?
Yes. The lower pH of the final product used in the cleaning process helps to seal off the hair; sealing the hair means fibres are smoothed down and moisture is held in better.
What does this mean for your hair regimen?
It is much better to use products in the same product line as they are designed with this fall in pH from initial to final product in mind.
What is the pH of relaxer and permanent hair colouring agents?
They are all alkaline with a pH ranging from 10 to 13.
What is the consequence of using these strongly alkaline products in hair?
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What happens to hair at different pH levels?
Reference: The Science of Black Hair, pages 44-45
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