Page 146 - Chapter 3 - An Introduction to Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 1st Edition
Treating over tattoos or damaged skin
It should be emphasised that all laser/IPL treatments of hair should only be carried out on ‘normal’ skin. Do not treat over tattoos – you WILL induce tissue damage. Likewise, don’t treat in areas where the skin is damaged or diseased in any way. Better safe than sorry!
SHR – How can it work properly?
The original study (Royo J., et.al.) which looked at the SHR technique applied a diode laser at the skin in relatively small areas – about 10 by 10cm squares. The laser emitted pulses at a relatively low fluence (5 to 10 J/cm2) in pulsewidths of 10 and 20ms, at 10 Hz (10 shots per second) and the laser head was scanned at the appropriate speed over the skin surface (around 10 cm/sec). This allowed for an evenly distributed series of laser pulses to heat both the dermis and hair follicles.
Most patients displayed “intense” erythema (reddening) and perifollicular oedema (swelling). They observed that, in 368 test subjects, they achieved a ‘good’ or ‘very good’ response in 289 of them, based on their own, subjective, evaluation.
However, it appears that this technique was severely altered in later years, by many manufacturers/suppliers. It has been sold as a ‘pain-free’ due to the relatively low fluences used. The problem arises when large areas are treated using this technique – the researchers point out that the dermis builds up heat during the treatment which raises its temperatures by a few degrees. This, coupled with the high temperatures in the follicles, leads to a good clinical outcome.
If larger areas are treated by this method, then the dermis may not attain the same temperatures as were found in the original study. The chances of success, therefore, drop significantly. We feel that many people applying the SHR technique are unaware that they are applying it incorrectly!
Discussions with many users across the planet reveal that more consistent results are easily achievable if the following criteria are adopted (with a diode laser):
Table 36 – Suitable ranges for the SHR technique
It appears that using a slightly ‘slower’ frequency, between 3 and 7 Hz, is easier to apply with more consistency. In addition, smaller areas should be treated, as used in the original study, rather than large areas like legs!
________________________________________________________________________ 146 Chapter 3 Laser/IPL Hair Removal
© The Laser-IPL Guys, 2022
Setting
Range
Fluence range (J/cm2)
5 – 30
Pulsewidth range (ms)
40 – 100
Frequency range (Hz)
3–7