Page 67 - Mike Murphy's Blog Posts

Of the remaining 50%, a relatively small portion is absorbed in the hair melanin. Most of the rest of it will be absorbed in the dermis where it will be converted into heat energy. This is not good! This will cause the temperatures in the dermis to rise, potentially damaging those tissues, and may lead to scarring.
“Cooling is critical”
What this means in reality is that we must mitigate against all this excess heat energy in the dermis, before, during and after treatments. We do this by applying a proper level of cooling – contact cooling is the most efficient. Air cooling is fine but surface contact cooling with ice packs is at least four times more efficient at removing the excess heat energy.
Proper cooling will not only minimise any potential tissue damage but it will also improve the comfort level for the patient. In addition, it allows for higher fluences to be used, which may be required in certain procedures (such as for deeper follicles).
We need to realise that we are deliberately over-heating the skin in all of these photothermal treatments – so we must balance that over-heating with plenty of cooling. The calculations above reveal that when we treat hair (and, it turns out, blood vessels too!!) we are mostly heating the skin – the treatment of the hair is almost a “by-product”!
So, be sure you apply plenty of cooling to your patients’ skin – they will certainly appreciate it.
I hope this surprised you – it certainly did me!
Ciao for now, Mike.
Mike’s Blog Posts 67