Laser removal of the unwanted hair is one of the most popular cosmetic procedures. Speed of hair removal, minor pain and continuance of the effect the lack of hair growth make laser hair removal a very popular procedure. Thit is why almost all manufacturers of laser technologies try to offer devices for this procedure.
The mechanism of laser and photo hair removal based on the effect of selective photothermolysis, which lies in the fact that melanin of hair absorbs the energy of laser radiation, converts it into heat and transfers it to the structure of hair, causing coagulation. There are a few problems lying in the way of this mechanism.
The main problem is a patient’s skin pigmentation level because melanin is a main chromophore through which can be realised the hair removal mechanism; this exists not only in hair but also in skin. With that, the probability of radiation absorption by melanin of skin does not differ from that of absorption by hair. Moreover, if we consider the fact that the hair has a very small size compared to the laser spot on the skin, it becomes clear that the bulk of the laser radiation will be absorbed not by melanin of the hair but by melanin of the skin.A consequence of this is the skin heating up to coagulation.
The first laser epilators were made on the basis of a ruby laser. Efficiency of absorption of ruby laser radiation (694 nm) is significantly higher efficiency of absorption of radiation than other lasers operating in the “transparency window” of the skin. However, little by little, people started to refuse these lasers because a high coefficient of absorption by melanin has a reverse side. Radiation absorbs more efficiently by melanin of epidermis which leads to its overheating and shielding hair from the influence.
Later, for the purpose of hair removal people started to use neodymium, diode and alexandrite lasers. Efficiency of absorption of these lasers is lower than that of ruby, so to provide transferring to the hair the dose of energy, sufficient for its coagulation it’s necessary to significantly increase laser pulse energy. The result, as is clear from the above, is increased skin heating. If we also take into account the fact that in case of less effective absorption of this radiation by melanin, depth of its penetration into skin increases, we can see that in this case excessive heating of the surrounding tissues can with a high probability lead to scarring.
Using of additional cooling devices to ensure the “comfort” procedure, not only does not solve this problem, but on the contrary, increases the risk of scarring, because you can only cool the skin surface, and scarring occurs when overheating deep layers of the dermis.