Page 127 - Chapter 3 - An Introduction to Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
fluences to ensure a denatured volume of at least 99% of the germ cells, which should always generate good results.
It must be remembered that these are ‘general’ fluence suggestions – in some cases you may require more fluence to reach deeper follicle germ cells.
As in all cases, sufficient cooling must be utilised to protect the skin properly – see next Section.
Skin Cooling
As was discussed in a previous section, the applied skin surface cooling is critical in protecting the epidermis and upper dermis. It also reduces the pain sensation felt by patients/clients, plus it helps to reduce blistering and skin discolouration.
There are three important ‘stages’ in effective cooling:
Pre-cooling
It is very important to ensure that the epidermis/upper dermis are sufficiently pre-cooled prior to firing the laser/IPL energy. By reducing the temperature of the thermal pain nerve endings (just below the basal layer) it is possible to significantly reduce the pain felt.
We recommend using ice-packs placed on the skin surface for around 20 to 30 seconds before administering the light energy. For deeper follicles (bikini and underarms) you may wish to increase this time.
Fire the light energy at the skin as soon as you remove the ice-packs – the skin will quickly become warm due to its blood supply.
During
The cooling while applying the light energy will depend on the system you are using –
IPL/diode lasers typically employ a cold tip which can be placed on the skin surface during treatments. This will help to maintain a cold surface.
Nd:YAG/alexandrite lasers usually do not make contact with the skin surface and so use external devices such as forced air-cooling or cryogenic systems. These may be built into the laser handpiece or separate.
Post-cooling
As described before, more than 90% of the light energy fired into the skin is not absorbed by hair melanin (this is after losses due to back-scattering and transmission). Consequently, this energy is available to heat up other tissues in the skin. As it diffuses towards the skin surface, it will meet the skin-air boundary. Given that air is a really poor heat conductor, most of the heat will simply remain in the skin.
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