Page 54 - Chapter 3 - An Introduction to Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
In fact, water has a thermal conductivity of around 0.6 Watts/mK, while air is only 0.025 W/mK. So, we can see that water conducts heat at around 24 times faster than air. When we generate heat energy in the dermis, which is 70% water, some of that energy will flow towards the skin surface. When it meets the air (at the skin surface), most of it will simply return back into the skin, because the conductivity of the dermal water is much greater than the conductivity of the air. The skin surface effectively acts like a heat mirror – it reflects most of the heat flow back into the skin – precisely where we don’t want it!
If we put some water-based gel on the skin surface, then the heat will readily conduct into that gel. If that gel is very cold, near-zero degrees Celsius, then the heat will prefer to flow to that point rather than back into the skin. This explains why active skin surface cooling is so important.
There is a specific technique which can be used to properly cool the skin...
Pre-cooling
Apply some cold gel to the skin surface and then place a cold tip to the skin surface for around 2 to 5 seconds before firing the laser/IPL – this will lower the temperature of the epidermis and upper dermis, protecting them from the excess heat. In particular, this will reduce the risk of damaging the epidermal melanin in the basal layer.
With IPLs and diode lasers use the cold tip to keep the skin cool During whilst firing the energy pulse. With other systems with no contact
cooling, apply forced air or similar, to keep the skin cool.
If using a cold tip, keep it in contact with the skin for a few seconds
after the pulse has been fired. The skin now has a lot of excess Post-cooling heat in it and the laser/IPL cold tip is an excellent tool to remove
much of it.
If not contact cooling is available, use ice packs.
Apply ice packs, or similar, to cool the whole area immediately
after the treatment. If treating a large area (such as legs) use a After number of ice packs – place these on the skin during the
treatment process – don’t wait to the end of the treatment – it’s too late by then!
Table 11 – Cooling of the skin in LHR treatments
________________________________________________________________________ 54 Chapter 3 Laser/IPL Hair Removal
© The Laser-IPL Guys, 2022