Page 33 - Blog Posts v1

The depths I used here are for the bulge, where the stem/germ cells reside on the follicle wall surfaces.
These fluences assume a pulsewidth between 2 and 12 ms. Shorter, and longer, pulsewidths will not work so well – the cooking is less efficient! I have also assumed a wavelength range between 600 and 1200 nm in these calculations. A smaller range will require higher fluences.
Obviously, deeper follicles (bikini, armpits) require more fluence at the surface to ensure sufficient light gets deep enough to heat them. This means that more pre-cooling is also required, to protect the epidermis.
Body Area
Threshold fluence (J/cm2)
Upper Lip
20
Chin/Arms
28
Arm pits/legs
33
Bikini
36
Interestingly, a small increase in fluence (i.e. 1 J/cm2) above these threshold makes a large difference in terms of cell destruction! But, fluences below these levels will merely destroy some of the stem/germ cells, meaning that finer hairs will likely grow back in the future.
These are my first set of calculations – they may change as I delve deeper into this study. But, I know from clinical experience that the numbers above make sense, for those pulsewidths.
I plan to generate further sets of these fluence/pulsewidth combinations for diode, alexandrite and Nd:YAG lasers in the near future. I will be discussing all this stuff in much more detail in my MasterClasses.
Hope this helps, Mike.
Mike’s Blog Posts 33