Put simply, yes, excessive or improper use of heat styling tools can indeed lead to damage in the hair’s structure. But understanding the underlying mechanisms of heat-induced damage means we can make better choices about our hairstyling practices for our hair!

The Science of Hair Structure

Each hair on your head is made of three layers: the medulla (innermost layer), cortex (middle layer), and cuticle (outermost layer). The cortex, responsible for hair’s strength and elasticity, is primarily composed of keratin protein. The cuticle, a protective layer of overlapping scales, safeguards the cortex.

What happens when you add heat to your hair?

  1. Hair loses its resilience and strength because intense heat can dry out the outer protective layer, causing small breaks. This makes the hair dull, dry and often appears lighter.
  2. After the protective layer is damaged the cortex becomes vulnerable. When this is subjected to high temperatures, the protein structure (keratin) is altered (called denaturation) losing its natural structure and causing damage, like becoming brittle.

Temperature matters

Studies show a critical temperature of 140 degrees C is key. Below this temperature little modification of the hair structure was observed, above this is where damage to the protective cuticle and deeper structures started.

Is all hair vulnerable?

Hair that is already chemically processed is more vulnerable to damage when heat styling. However, healthy hair can tolerate heat without too much concern, as long as the hair is being well looked after. This is great, because it means we can continue to heat style as long as we are doing the right things in-between.

In our next blog we will explain how to look after your hair for heat styling health!!

Some of the literature