Page 20 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
13. Unfortunately, we cannot target the stem cells directly using light – they have no optical targets (chromophores) we can direct the light at specifically. That’s why we use melanin in the hair shaft and the bulb – it is a ‘conduit’ to generate heat. This heat energy will naturally diffuse (or conduct) out towards the stem cells, over time.
14. The whole point of these treatments is to raise the temperatures of the stem cells to a sufficient level and for a sufficient time to ensure that they are ‘cooked’ thoroughly.
15. If enough light energy, of the correct wavelength (colour), is delivered to the skin surface over a suitable time, then we can selectively heat up the target hair follicles, without over-heating the rest of the skin (especially when using a suitable level of skin cooling).
16. The first treatment of any body area should generate the ‘best’ results, since, on the first treatment occasion, the maximum number of anagen hairs are presented. With each subsequent treatment, the number of anagen follicles decreases, simply because there are fewer of the follicles left to go back into the next anagen phase.
17. The total number of repeat sessions depends strongly on the interval between treatments. A computer model has shown that leaving longer gaps between sessions results in fewer overall treatments, as long as the correct dose of fluence is applied!
If we can cook the stem cells sufficiently well, they will die. If all the stem cells in a follicle are destroyed, that follicle cannot regenerate – it is dead! We are born with around 5 million follicles – we do not grow any more over time. If we can kill 1 million of them, then there will be only 4 million left.
So, it basically comes down to two things....
Fluence and cooling
There are, essentially, two sides of the same coin. We must find the correct fluence to kill the follicles with heat, but it must be balanced by the correct amount of cooling to minimise unwanted damage and pain.
That’s all there is to it! Quite simple really. Except, it’s not quite that simple....
________________________________________________________________________ 20 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
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