I’ve seen a lot of videos, recently, where laser operators are showing their prowess with laser hair removal, usualy with a diode laser. However, most of them are doing it wrong!!
They are usually seen ‘scanning’ up and down an area, relatively slowly, firing off a whole bunch of pulses of laser energy.
Unfortunately, this will most likely be pretty useless leading to hair regrowth and fine hairs replacing thicker ones. Plus lots of excess treatment sessions…
So, what are they doing wrong?
The SHR Technique
This technique was originally developed by a laser doctor in Vancouver, Canada – Martin Braun – in 2009 to find a ‘painfree’ way of treating hair using a diode laser at low fluence.
His technique (SHR is technique; NOT a technology!!) was to apply a sequence of 10 J/cm2 pulses at 10 shots per second in a relatviely small area, approximately 10 x 10 cm, using a constant motion so that this area required between 6 and 10 passes.
This is an interesting approach because my calculations show that 10 J/cm2 is below the threshold fluence necessary to kill hair follicle germ cells. It’s simply not enough energy! But, by effectively building up the temperature in that small(ish) area, using multiple pulses, the follicle temperatures do achieve a suitable temperature by the end of the procedure.
Dr Braun’s idea was that by keeping the fluence at such a low level, the pain felt by the subject would be limited. However, the desired end-result would still be achievable by accumulating those laser pulses.
He also treated other areas using the more conventional ‘stamping’ technique, for comparative purposes.
You can read his report here – it’s well worth a read.
Results
His results showed that his SHR technique compared very favourably with the stamping technique, with lower incidences of pain.
However, he also claims that there was no significant difference in the final outcomes of each technique – one is not any better than the other!
But, he missed something very important in this study, in my opinion. He neglected to investigate the effects of proper skin surface cooling.
The Importance of Cooling
The main reason why laser hair removal is painful is due to the high temperatures attained in the epidermal melanin as the light energy passes through to the deeper follilces. I discussed this in a previous post.
The skin’s pain receptors are located just below the epidermal/dermal junction and usually sit at around the normal dermal temeprature of 37C. They trigger pain signals to the brain when they reach 45C – only an 8C increase! It doesn’t take much laser/IPL energy to induce that much of an increase.
The solution is to pre-cool the epidermis before applying the light energy. Using icepacks or cooling devices can reduce the pain receptors temperature by more than 10C, or more, with ease. This allows for higher fluences to be applied with less likelihood of triggering pain.
Cooling should also be applied after the treatment too because most of the light energy is not used in the hair removal prcoess – it is ‘swimming’ around the demris looking to heat, and damage, something…
Conclusion
The SHR is a good technique for laser/IPL hair removal – but ONLY if it is applied correctly!! The treatment area must be limited in size to allow the heat energy to build up, and allow the germ cells to reach the desired temperature.
If a long, sweeping motion is used, the germ cells will have cooled too far before the next energy pulse is delivered. They will simply never become hot enough. The final results will be poor.
Alternatively, the stamping technique can be applied very successfuly, with either lasers or IPLs, as long as good skin surface cooling is also employed.
I hope this helps, but, no doubt, I’ll probably come back to this subject at some point…
Mike.
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