Page 130 - Chapter 3 - Laser/IPL Hair Removal

The ‘Kill-Stun-Null’ Zones
Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
Monte-Carlo simulations reveal that this increase in fluence can extend as far as 1.4mm into the skin (for red and near-infrared light). This means that the fluence applied at the skin surface will increase down to a depth of 1.4mm, then will drop rapidly due to absorption and scattering.
Many laser operators complain that their treatments are ‘ineffective’. They say that hairs regrow after some time, often lighter and finer. What is the reason for this?
Essentially, it all comes down to fluence – or, rather, the lack of fluence! We realised that we need to visualise the skin as a sequence of 'zones' -
the 'kill' zone where the hairs will always be successfully destroyed; the 'stun' zone where the follicles are stunned but not properly killed; and the 'null' zone where nothing much happens to the hairs.
This idea applies to everything we treat in the skin - blood vessels, tattoos, dermal pigmentation etc.
________________________________________________________________________ 130 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
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