Page 77 - Chapter 3 - Laser/IPL Hair Removal

Arm Pits
Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
Persistent erythema
Careful depth control
Vascular light treatment
2-6 months
Table 13 – Dermal Complications following light treatment of the skin
Dormant Follicles
In virtually all situations you will encounter ‘dormant’ follicles. These usually don’t become active until triggered by something – trauma, hormonal changes, medicines etc. No light-based therapy will affect these follicles, until they are active.
As a consequence, we can never guarantee a “100% removal” simply because the dormant follicles may begin growing at any time after the treatment.
Thick and thin hair – how much light energy do they absorb?
How thick is a hair? Well, according to some research by physicist, Brian Ley (they do all the best research!!!), it ranges between 17 and 181 microns in diameter (see his results here). That is between 0.017 and 0.18 mm. (Note – other researchers have found a slightly different range of diameters).
So, that means that their cross-sectional areas [Area = 𝜋 x (radius)2] are between 0.0000023 and 0.00025 square centimetres!! Hairs are very small...
According to the data in Table 14, the number of hairs per square centimetre varies enormously across the body, from as low as 60 on the legs and thighs to around 880 on the cheeks.
30 70 10 52 2-4 500 70 30 12 16 3.5-4.5 65 80 20 16 12 2-4 80
Table 14 - Data from Richards & Merhag
________________________________________________________________________ 77 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
© The Laser-IPL Guys, 2025
Body Area
Chin
% Resting Hairs Telogen
% Growing Hair Anagen
Duration of Telogen (weeks)
Duration of Anagen (weeks)
Follicle Depth (mm)
Follicle Density (per cm2)
35
65
6
8-20
1-2.5
500
Upper Lip
70
30
12
16
3.5-5
70
Pubic Area
Arms
Legs & Thighs
80
20
20
16
2-4.5
60
Breast
70
30
12
8-12
2-4
65