Page 184 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
If there is insufficient energy delivered, then only some of the target stem cells will be properly (irreversibly) cooked. Some may survive and regenerate. Other deeper cells may not be affected at all!
The difficulty is that we can never know how deep these cells are. If the hair is deep (such as underarm or pubic hair) then the stem cell bulb will be correspondingly deeper compared with more superficial hair. In these cases, we must deliver more energy to ensure a sufficient amount reaches those cells. Unfortunately, the concentration of this energy (fluence) drops approximately exponentially (after a certain depth) as it penetrates deeper into the dermis (due to scattering).
So, what often happens, is that only a portion of the stem cells in a bulb are cooked properly, leaving a sufficient number to ‘re-group’ and take the follicle into the next anagen phase. But, since there are now fewer stem cells than before, the new hair is thinner (finer). Fine hairs do not generally contain as much melanin as thicker hairs since the hair shaft is also thinner.
As a consequence, fine hairs are harder to kill than thicker hair!!
When we hear someone saying “the hairs have grown back finer and lighter”, we immediately think “you didn’t use enough fluence!!” It’s obvious! Lighter, finer hairs require even more fluence since they have less target melanin in them. The pulsewidth is not really that important (contrary to popular opinion!) It is the total ENERGY which drives these processes – always.
Insufficient energy will always result in poor results. Using the correct fluence at the start of your treatments should always generate good results. And NEVER start treatments with ‘low’ fluences and increase them each time your customer returns – that is an absurd, and detrimental, idea!!
Figure 104 - Higher fluence deliver more energy to deeper parts of the dermis, which should be able to properly cook those pesky stem cells
In the above figure, the higher fluence has now enveloped the stem cells successfully. If there is sufficient energy, then those cells should cook properly, i.e. irreversibly. That follicle is now dead and cannot regenerate.
________________________________________________________________________ 184 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
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