Page 71 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
Figure 34 - A higher fluence will ensure more energy reaches the deeper parts of the follicle, thereby increasing the likelihood of a successful outcome. However, it will also induce more thermal pain due to greater absorption in the basal layer.
Finally, a ‘high’ fluence is inflicted on this follicle. It appears that now we have sufficient fluence at the bulge depth, leading to a much greater degree of heating in that region.
If enough fluence has been delivered, then we can be sure that the cooking process will kill virtually all of the stem cells in both the bulge and the bulb, which will result in permanent follicle death.
That follicle is now toast!
However, the temperature of the pain receptors may now be high too. This is why we need to apply plenty of pre-cooling before the light energy is fired at the skin. If the pain nerves are suitably cold, then the rise in temperature will hopefully keep the maximum value below 45C, thereby minimising any painful sensations.
A higher fluence will induce higher temperatures in the pain receptors leading to more pain. Surface cooling is required to minimise this problem.
Now the fluence has definitely reached the bulge and the bulb and induced more heating in the stem cells. However, this may result in only a portion of those cells being properly cooked.
The remaining cells will survive and regrow a new, finer hair in the next anagen phase. That thinner hair will contain less melanin than before, simply because it is smaller in volume.
This occurs with many laser/IPL operators across the world. They are simply using too low a fluence to generate the desired response in the follicles. Lighter-coloured, finer hairs re-growing is inevitable.
Figure 35 - A ‘high’ fluence will ensure plenty of energy reaching the stem cells in the bulb. But, it will also generate much higher temperatures in the basal layer. Pre-cooling is critical!!
________________________________________________________________________ 71 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
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