Page 27 - Blog Posts v1

In reality, we should consider the following:
The fluence MUST be chosen to match the colour and depth of the hair;
the skin colour MUST dictate the amount of surface cooling!
The fluence applied to the skin surface should NEVER be set according to the skin colour – that defeats the whole purpose of the treatment. And yet, many of today’s devices are programmed to do precisely this.
Why?
It’s because the manufacturers want to reduce the risk of you damaging your patient’s skin – which is fair enough. But, by reducing the fluence, they are also reducing the chances of success!
What they should be telling you is that darker skins require much more cooling than lighter skins – before, during and after the treatment.
I calculated the temperature in light (SC1) and very dark (SC6) skins when hit with a 20 J/cm2 fluence at the surface. I looked the difference between the alexandrite, diode and Nd:YAG lasers.
Notably, maximum temperature achieved for the palest skin colour (SC1 with a melanin concentration of less than 10%) is marginally above the background dermal temperature of 37oC.
However, in very dark skin (SC6 with a concentration of >43%) the temperatures range from 54.4oC for the Nd:YAG laser to 184oC for the alexandrite laser! It was 133oC for diode lasers (see figure 1).
Obviously, all the other skin colours are between these two extremes.
So it is very clear that while all the current hair removal lasers are perfectly fine when treating very pale skins, only the Nd:YAG should really be consider safe when treating black skin.
Mike’s Blog Posts 27