Page 138 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
Pre- and post-cooling
As mentioned above, we must pre-cool the thermal pain nerves (nociceptors) before firing any light energy at the skin.
The main thing to remember here is that we must make sure that the pain nerves are cold – at least 15 to 20C colder than the surrounding dermis – to minimise any painful sensations. This not only requires a cold contact at the skin surface, but it must also be in contact for a suitable time too.
Table 25 - The ratios of hair colour to skin colour in skin tones SC1 and SC6
Mike ran his thermal program to see how ‘effective’ skin surface cooling is in the epidermis and dermis (Figure 80). In this graph, we can see that the temperature drops rapidly at the skin surface (blue curve) when exposed to an ice pack, while it drops more slowly at 1, 2 and 3mm deep.
After two minutes of surface cooling, the skin surface has reached around 2C, while the deeper regions have reached around 7, 12 and 15C, respectively. The thermal pain receptors are found just below the epidermis, so their temperature will also reach down to around 2C after two minutes exposure to ice packs.
________________________________________________________________________ 138 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
© The Laser-IPL Guys, 2025