Page 59 - Chapter 3 - An Introduction to Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
Figure 21 – The real target in the hair follicles are the germ/stem cells found in bulges on the follicle walls
The minimum fluence that would provide permanent hair reduction (i.e. complete destruction stem cell volume) is in the range of 9-11 J/cm2 for very dark hair on pale skin (for diode and alex lasers and IPLs) – but this is only for shallow follicles (this is 25 J/cm2 for Nd:YAG lasers). Higher fluences are required to successfully destroy deeper follicles, such as those found in the arm pits or bikini areas.
Hair depth and fluence
It is obvious that the depth of hair follicles range across the body quite significantly. In the upper lip they are typically between 1 and 2.5 mm deep, whereas in the axillae (arm pits) and bikini regions they may be up to 5 mm deep.
This means that we must consider using different fluences when tackling different regions of the body. If a fluence has been chosen for the upper lip, to reach follicles at a depth of 2.5 mm, then this fluence will not be sufficient for a bikini or axillae region – the fluence will simply not be enough to heat up those follicles properly!
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