Page 183 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
The fluences on the table above are those required to effectively denature stem cells down to a depth of 4mm – this appears to be the deepest depth which human follicles may reach (Uno). As we can see, these numbers are pretty high! Even with excellent skin cooling, many patient/clients may not be able to tolerate such high fluences. This is particularly true for darker skinned people who will suffer higher temperatures in their basal layer.
However, it should be remembered that the success rate depends on the applied fluence. Lower fluences will not deliver sufficient energy as deeply as high fluences, but they will still have the desired effect – down to some depth. The success of these treatments is essentially based on the fluence-depth relationship.
The higher the fluence, the deeper the effectiveness.
Why do ‘finer’ and ‘lighter’ hairs appear after laser/IPL hair removal treatments?
All hairs are part of a follicular unit which comprises the hair shaft, melanin (not always!!) and germ/stem cells. [There are other components such as the pilo-sebaceous units – but we’re not interested in those here.]
The stem cells are responsible for initiating and growing the hair in the anagen phase. They reside in the ‘bulge’ which is usually located about one third to one half of the way down the follicle, and in the bulb which varies according to the phase.
In order to kill a follicle, ALL the stem cells in that unit must be destroyed (denatured). We can do this with heat generated by the absorption of light. However, to ensure full, irreversible denaturation of all those stem cells, we MUST deliver sufficient energy to reach the deepest parts of the bulb – it is the heat energy which ‘cooks’ the stem cells.
And this is where the problem lies...
Figure 103 - Low fluences have little effect on deeper targets simply because there
________________________________________________________________________ 183 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
© The Laser-IPL Guys, 2025