Page 30 - Mike Murphy's Blog Posts

I use the same numbering system as the Fitzpatrick Scale since this is very familiar to many people. But, as we can see, if you go on holiday and come back with a tan, your melanin concentration will increase – changing your ‘skin colour’. However, your Fitzpatrick number doesn’t change!!
So, having now defined the actual skin colour, how can we calculate the risk of injuring the epidermis with light energy?
To do this, we need to setup a framework. I chose the maximum risk when the alexandrite laser is used on black skin – that is, 755nm on a 43% melanin concentration. This combination yields the highest possible melanin absorption coefficient (how ‘strongly’ the light is absorbed by the melanin).
Out of all of today’s devices and skin colours, this is the ‘riskiest’ possible option! So, using this as the ‘maximum’ risk, it is possible to calculate all the other scenarios, based on this worst-case scenario.
In essence, the values in the graphs above, show the ‘relative’ risk of epidermal melanin damage compared with the alexandrite/black skin scenario. (If anyone can come up with a better idea, please let me know.)
I have also assumed a typical wavelength range of 600 to 1200nm for the IPL treatments, which yields an averaged absorption coefficient similar to that of the diode laser.
Mike’s Blog Posts 30