I have been invesitgating the removal of hair by laser and IPL for about 427 years. But recently, I figured out something quite important in the growth cycle.
Histological research shows that the matrix cells, which envelope the dermal papilla cells at the base of the follilce, grow in both size and melanin concnetration as the bulb descends towards the sub-cutis – see image.
This means that one of the targets for our light energy – melanin in the matrix – increases as the follicle grows, particularly in anagen III (when most of the folillce growth occurs).
Rather bizarrely, this means that it is actually easier to hit that deeper target as the growth progresses. This is highly counter-intuitive. We have all been told that deeper hiars are more difficult to heat properly, precisely because of their depth – not much light can get down there.
It turns out that the increase in size and melanin concentration ‘beats’ the drop in fluence with depth. In other words, the larger, darker, deeper target in actually easier to hit, with light energy!!
I am continuing to develop a new optical-thermal model to invesitgate how this translates to required fluences etc. My ‘fluence app’ already contains most of this. See my previous post on this – https://mikemurphyblog.com/2026/09/06/new-fluence-recommender-app/.
Watch this space…
Mike.
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