With the impact of laser radiation energy is absorbed and produces heat, which the temperature reached produce the biological effect described in the previous relationship. But, immediately, this heat is dissipated. The dissipation is done differently in the various structures: the skin more slowly and more rapidly in the follicle. As the irradiation of both structures was performed at the same time, it is important to distinguish these two behaviors.
Faced with an onslaught of Laser:
* the skin is heated less and takes longer to cool;
* the bulb absorbs more laser radiation, heated, and it takes longer to cool.
This effect can be quantified through the concept of TRT (Thermal Relaxation Time, or thermal relaxation time), at which time the tissue in question has removed half of the heat energy produced by the laser impact. This time is for the epidermis in general, 8 to 10 milliseconds, and the pilo sebaceous follicle, from 20 to 60 milliseconds.
If we apply an impact of sufficient energy, with a single shot can destroy the bulb, but also heats the epidermis, the amount of melanin present.
The purpose of hair removal is to have a laser unit powerful enough, with an impact, getting the destruction of the follicle, affecting skin to a minimum.
