Page 70 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
Figure 32 - The real targets are the stem cells. These are found throughout the follicles, but mostly in the bulge, near the surface, and in the bulb, at the base of the follicle
A ‘low’ fluence will induce some heat in the pain nerves, which will lead to a slight rise in temperature. If the temperature stays below 45C, then no pain will be felt.
However, this fluence has not induced any heating in the bulge or in the bulb. The stem cells may become slightly warm (due to conduction from above), but nowhere near hot enough to cook irreversibly.
Such a low fluence will have very little effect on the follicle.
The bulge and the bulb are where most of the target stem (or germ) cells are located in the follicles - around 1.5mm deep in the bulge and down to 4mm in the bulb.
We must deliver enough light energy to that depth, to ensure a suitable temperature rise there.
Note that the thermal pain receptors (nociceptors) are located immediately below the epidermis.
Figure 33 - A low fluence will only denature stem cells close to the surface. There is simply insufficient energy in the deeper regions to properly denature the targets
________________________________________________________________________ 70 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
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