Page 25 - Chapter 3 - Fundamentals of Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
The Epidermis and Skin Colour
The epidermis is the outermost layer of the skin and can have a significant effect on any light- based hair removal treatment. Hair follicles are deemed to be ‘indentations’ into the epidermis and a reformed during embryo development.
We discussed skin colour in some depth in Chapter 1 – please read that section. Here, we will discuss more about this topic as it relates to hair removal.
The most important chromophore (light absorbing targets), when considering hair removal, is melanin. This is what gives us our skin, and hair, colour. Most melanin is found in the basal layer of the epidermis (at the dermal/epidermal junction) and in the hair shaft. Melanin can absorb light of many colours (wavelengths) from the ultraviolet through to the infrared (Figure 2).
We can see from Figure 2 that melanin absorbs very strongly at the blue end of the spectrum (350nm) but this drops as the wavelength increases. The absorption above 700nm is relatively low, yet, as we will see later, most lasers used for hair removal operate at wavelengths in the infrared region!
Why is this? Well, there is a good reason for this. When dark hair is targeted using lasers/IPLs, the concentration of melanin is significantly greater than in the surrounding epidermis. As a consequence, more light energy will be absorbed in the hair relative to the epidermis.
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