Page 169 - Chapter 3 - Laser/IPL Hair Removal

Chapter 3 – Fundamentals of Laser/IPL Hair Removal 2nd Edition
shortly after the tests. If this occurs, trust the science!! If you are applying the correct level of fluence and pulsewidth, then you should achieve the desired result.
If no endpoint is visible then you may wish to ask further questions of your client/patient – especially regarding exposure to the sun or sunbeds. Perhaps they have changed/started new medications which may affect their skin’s response. There may be other external influences which you are not aware of. Clients/patients are notorious for not yielding new information after the initial consultation – it is imperative that you continually check with your clients/patients for any new relevant information such as many new medications, recent sun tans, newly diagnosed conditions, upcoming holidays, amputations etc.
A good report on this topic is “Immediate skin responses to laser and light treatments: Therapeutic endpoints – How to obtain efficacy” by Molly Wanner et.al. (See References).
In some cases the surface hairs can be seen to vapourise – small puffs of smoke are visible. This is fine! It merely shows that the melanin in those hairs have absorbed sufficient energy to destroy them completely, However, this does not necessarily mean that the final result – destruction of the follicles – is guaranteed. It does generate a ‘burned hair’ smell in the treatment room, which has been found to be potentially hazardous! (See Section 3.2 - ‘Plume in the Air’.)
In summary, for most situations with laser/IPL hair removal, we are looking for some erythema and a little oedema within a few minutes of the treatment exposure. Cooling should always be applied soon after the treatment to help reduce these effects and any pain.
Threshold Denaturation Fluences – Four Devices
What are the threshold (minimum) fluences required to destroy hair follicles?
This is not easy to determine! It depends on the type of device you are using – IPL, diode, Alexandrite, Nd:YAG laser. It also depends on the depth of the follicles and on the hair colour. We built a computer model to try to calculate these fluences. It considers all of the above for each device. First, we should consider what we are actually trying to do...
To effectively kill hair follicles, we need to essentially ‘cook’ the germ/stem cells, irreversibly, so that they cannot regrow. To achieve that, we must apply a certain amount of energy over a certain time – just like any cooking process!
So, we need to find the minimum amount of heat (light) needed to cook these cells properly.
IPLs – Threshold fluences
Our model allows us to apply different fluences over different pulsewidths to hair follicles at various depths. Here is what we found (for IPLs for an averaged wavelength, equivalent to
________________________________________________________________________ 169 Chapter 3, Ed. 2.0 Laser/IPL Hair Removal
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