Page 73 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
So, we must use higher fluences to achieve the end-goal – irreversible destruction of the stem cells. To do this we must be in the ‘danger zone’ – dangerous because this level of fluence is highly likely to damage other tissues in the skin (collagen, vessel, the basal layer etc) - Figure 36. Consequently, we must increase the cooling to balance this higher risk.
Melanin absorption – how they compare across devices?
In the skin:
First, let’s consider the absorption of light in melanin in the epidermis:
The graphs in Figure 37 show the melanin absorption curves for six skin colours – ST1 to ST6. These skin colours are based on the Steve Jacques epidermal concentration analysis and better reflect the optical properties of the epidermis. This is a far more accurate representation of the skin colour compared with the Fitzpatrick scale (which is, in reality, a ‘response to ultraviolet energy’ scale!)
Typical range of IPL wavelengths
Averaged IPL
Figure 37 – The melanin absorption curves for six skin colours
The absorption coefficients in the table above show clearly how strongly each wavelength is absorbed by melanin (both epidermal and in follicles). The IPL range, 600 to 1200nm, is fairly typical in many hair removal treatments.
________________________________________________________________________ 73 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
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