How does laser hair removal machine work?

Laser hair removal methods can be divided into three main categories:
1. Non-selective laser hair removal methods, such as carbon dioxide laser hair removal, are time-consuming and prone to scarring.
2. Photodynamic therapy, such as oral or external use of alpha-aminocaproylpropionic acid followed by laser. This method seems feasible in theory, but has few clinical applications.
3. Selective photothermal hair removal, i.e. hair removal with laser and intense pulsed light.
The principle of modern laser hair removal machines is based on the principle of “selective photothermolysis” proposed by American doctors Anderson and Parrish in 1983: a laser with a certain wavelength penetrates the epidermis, enters the dermis, and is selectively absorbed into the hair and hair follicles. Melanin molecules are absorbed and produce a photothermal effect, in which the thermal energy contained in the hair is transferred to the surrounding areas, completely destroying hair follicles, stem cells and other “hair roots”, resulting in permanent hair removal. The normal tissue around the hair follicles does not absorb this laser because it does not contain melanin molecules, so it is only slightly affected and does not cause signs of paralysis in general.