Page 57 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
which is about the thickness of ordinary A4 copy paper. There is no blood present in the epidermis as there are no blood vessels there.
The majority of side effects in light-based skin treatments are caused by skin burns due to overheating of the epidermis. Avoiding overheating of epidermal melanin is actually your biggest challenge in light-based treatments. The only way to control and avoid overheating of epidermal melanin is to:
A: Accurately measure the amount the epidermal melanin at the actual treatment site, on the day of treatment;
B: Provide consistent and depth selective cooling of the epidermis;
C: Understand the parameter settings of the specific light source used.
When skin is exposed to light a portion of the light will be absorbed in the epidermal melanin and heat it up. The more melanin, the shorter wavelength, the more heat. The absorption of melanin is very wavelength dependent. The shorter wavelength the higher absorption i.e. blue light creates much more heat in the melanin compared with red light at equal fluence and pulse duration settings, see graph below.
Figure 21 – The fraction of light absorbed by melanin depending on wavelength
We will later cover these three extremely important topics in detail later but first we will continue explaining the fundamental optical properties of the skin.
The epidermal melanin is a kind of optical/thermal barrier and too much melanin will set a limit in performing different types of treatments. In treatments of hair the light that has to reach the specific targets in dermis must pass through epidermis. It is obvious that a portion of the total light energy applied for these treatments will be lost as heat in the epidermal melanin. If the peak temperature in epidermis is higher than the peak temperature in the hair follicle then the treatment should not be performed since it will create unwanted skin burns.
All light must pass through the melanin in the basal layer of the epidermis. This will, inevitably, raise the temperature of that layer – which we must mitigate against.
________________________________________________________________________ 57 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
© The Laser-IPL Guys, 2025