Page 110 - Chapter 3 - Fundamentals of Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
Many operators ‘turn down’ their device’s output fluences on darker skins so that the treatment becomes more tolerable. But this will also reduce the likelihood of success! The best way to mitigate against pain and skin damage is to ensure proper, efficient skin cooling (see ‘Epidermal temperature rise due to skin colour’).
The curve in Figure 83 shows us how strongly melanin absorbs these wavelengths. This tells us how much light energy will be absorbed in the epidermal melanin too, and therefore, how much heat it might create there. Clearly, the alexandrite laser will generate much more epidermal heat than the Nd:YAG laser, for a given fluence.
It also means that more energy from an alexandrite laser will be absorbed in the epidermis compared with the other devices, leaving less energy available for absorption by the deeper hair melanin. Figure 83 also shows that an IPL output from 600 to 1200nm will also generate a lot of epidermal heat. By using a longer filter, say 700nm, this will reduce the pain sensation significantly. But it will also reduce the temperatures achieved in the hair shaft melanin. So, if an operator uses a 600nm filter, they need to mitigate against the extra heat on the epidermis by applying more surface cooling.
Cooling
We have discussed the importance of skin cooling in earlier sections. The main differences between these hair removal technologies is simple:
Device
Method
Diode laser
Contact cooling – cold tip
IPL
Contact cooling – cold tip
Alexandrite
Non-contact – air/cryo cooling
Nd:YAG
Non-contact – air/cryo cooling
Each has its merits, as discussed in the Section “Optimal Skin Cooling in Selective Photothermolysis”. With both diode and IPL systems the cold cooling tip is a part of the device, hence, it is ‘built-in’. But there is an issue with some of these devices – the cooling tips are only cold for a relatively short time. During usage, they can become warmer which reduces the skin cooling efficiency significantly.
With the alexandrite and Nd:YAG lasers, this is not possible. These systems will require an external skin cooling device – an air cooler or a cryo spray system. Some suppliers include these external units; some don’t.
As we said before, ice-packs are always a good idea – especially immediately after each session.
________________________________________________________________________ 110 Chapter 3 Laser/IPL Hair Removal
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