Mike Murphy's Blog

I just read a comment from a laser hair removal practitioner who was told, by a client, that she had been in another clinic and told that the “results would be better” if she opted not to use the cryogen. In other words, no skin cooling!

Clearly that laser tech does not understand what is going on in the skin!

So, I thought I’d explain it (again!!) in a very simple manner….

1. We fire light energy into the skin to heat up dark hairs, to try to kill the follicles.
2. The hair shafts become hot due to absorption of that light energy. The darker the hair, the hotter they become.
3. But, the melanin in the epidermis also heats up.
4. The thermal pain receptors are just below the epidermis – they trigger at 45°C.
5. Your normal dermal temperature is around 35°C, so it only takes a 10°C increase in temperature in the upper dermis to trigger pain!
6. If we cool the skin surface properly, including the pain receptors, there is a lower chance of pain.
7. By doing so, we can fire higher fluences at the hair follicles, resulting in better results, without pain.
8. Higher fluences will kill deeper hair follicles!! (Meaning fewer treatments required overall).

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In a nutshell, pre-cooling the skin is important – it reduces the pain, the risk of blistering and the risks of hyper- and hypopigmentation. Pre-cooling the skin does not affect the treatment outcome – darker hairs will always absorb much more light energy than the epidermis (the exception to this is when the skin is black – then the absorption in the epidermis is significant since the melanin concentration is so high!!).

If you don’t pre-cool the skin, your client/patient will feel much more of the heat (as pain!!). They will not appreciate it.

Plus, post-cooling is also important since a significant portion of the heat energy is essentially ‘trapped’ in the skin. It must be extracted quickly to minimise any unwanted thermal damage.

I wrote another post about the effects of higher fluences and how deep they can kill the follicles – https://mikemurphyblog.com/2024/04/03/the-kill-stun-null-zones-in-laser-ipl-hair-removal-why-some-treatments-dont-work/

Finally…

Proper skin cooling is critical in laser/IPL treatment of hair. Without it, you will induce pain and potential skin damage. With it, you will generate better results – always!! (I go into much more detail in this post – https://mikemurphyblog.com/2023/03/23/laser-skin-treatments-and-skin-cooling-should-we-do-this/).

Hope this helps,

Mike.

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