Initial interest in laser hair removal began when ruby laser used for tattoo removal was also noted to have a sustained effect on the hair follicles. The theory of selective photothermolysis holds that the thermal injury will be confined to a specific target if there is preferential absorption of the light at an appropriate wavelength and the pulse duration or width is shorter than the thermal relaxation time of the target. Thermal relaxation time is defined as the time it takes for the target to cool to fifty percent of its peak temperature.
The primary targets for laser hair removal are the hair follicle and the hair bulb. The endogenous target is melanin, which is located mainly in the hair shaft as well as in smaller amounts in the inner and outer root sheaths. Theoretically, laser or light energy directed primarily at the pigment of the hair shaft, melanin or the lotion, is absorbed and transferred to the surrounding follicle and perifollicular tissue, causing conductive thermal damage to the follicle. Adequate damage is required to cause long term hair removal. A better understanding of hair biology in the future should also produce other targets that may more efficiently cause hair removal.
Sorry, the comment form is closed at this time.