The hair is made of three layers: the cuticle, cortex and medulla.
The cuticle is the outermost layer and is made of five to ten overlapping scales with no pigment which are orientated towards the tip. This means they lie flat towards the hair tip, much like the tiles of a roof. The main function of the cuticle is to protect the hair. It acts as the ‘skin’ of the hair.
The cortex contains the hair pigment/colour and fibre bundles which contain keratin. This is the main part of the hair that will determine your hair colour, texture and the strength of your hair.
The medulla is the heart of the hair shaft but scientists are still uncertain about the main role of the medulla.
The natural pH of the hair is around 4.5 to 5.5. Much like the skin pH, it is acidic and using products that are not suited to this pH will damage your hair.
These microscopic images of a single hair shaft clearly show the differences in healthy and damaged hair. The first sign of damaged hair is raised cuticles. You don’t need a microscope to see this kind of damage either. Think of those images in shampoo commercials with long and shiny hair. If your cuticles are healthy and lying flat, then the reflection off the hair is more. Light reflects better off smooth surfaces that rough or uneven surfaces. It is no different with your hair.
Dull hair often has damaged cuticles that may be raised or partially raised. This scatters the light more and the hair will appear dull.
Once the cuticle is damaged, then the cortex is exposed. This then allows for loss of moisture and breaking of the chemical bonds that keep your hair strong. Once the cortex is damaged, it is often impossible to repair the hair and the only thing that helps is cutting the hair.
Hair, unlike the skin, is dead. We all hear this and it is a difficult thing to grasp. Once it leaves the hair follicle the cells are dead. Most hair products will coat the hair or work on repairing the cuticle.
For more on cuticle damage read Hair Bio Part 2