Page 47 - Chapter 3 - An Introduction to Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
Figure 16 – The nerve sensors in human skin
This layer is very thin typically around 60 to 100 microns (that is 0.06 to 0.1 mm). So, it can become quite hot but will lose its heat energy rapidly. Unfortunately, the pain receptor nerve endings are located in the epidermis and upper dermis, just below the basal layer (see image above). As the heat energy conducts into the upper dermis the temperature and pain receptors will be stimulated. NASA research has found that our temperature sensors will indicate heat up to around 45°C. Above that, they ‘switch off’ and the pain receptors kick in. This is to inform the brain that the temperature is approaching levels which could damage cells and tissue.
This is the main reason for pain during laser/IPL treatments. It is a direct consequence of the locality of the nerve endings in and just below the epidermal layer. The speed at which the heat energy conducts from the epidermis depends on its thickness. Darker skin will have more melanin in it, and so will conduct (lose heat) more slowly than lighter skin. Hence, darker- skinned individuals will likely feel more pain than a lighter-skinned person, for exactly the same light energy input.
Pre-Cooling
For this reason, the concept of ‘pre-cooling’ is absolutely critical in reducing the pain sensations felt during treatments. By reducing the temperature of the epidermal layer before delivering any light energy, any subsequent heating will induce a lower peak temperature, thereby minimising the pain felt.
We covered this topic in one of our blog posts. We cannot stress highly enough the importance of pre- cooling. Not only does it reduce the pain during treatments, but it will also reduce the likelihood of unwanted tissue damage in that region of the skin.
________________________________________________________________________ 47 Chapter 3 Laser/IPL Hair Removal
© The Laser-IPL Guys, 2022
The basal layer between the epidermis and dermis contains many melanocytes and melanin granules. Over time, these melanin granules migrate towards the skin surface. Darker skin contains many more melanin granules throughout the epidermal layer compared with lighter- coloured skin. As a consequence, the epidermis can absorb a significant amount of light energy in the visible part of the spectrum.