Intense Pulse Light is the device that generates heat energy by xenon lamp. The heat energy is absorbed by hair melanin and damages hair shaft to inhibit growth. Melanin is found in follicle epithelium and on epidermis as well, keeping this difference in view, IPL is designed to work in two different modes and energy levels. Dark and coarse hairs tend to absorb more light, whereas blonde or light hairs may take time to have effective results.
The spot head cover broader area of skin and allows the light energy to be absorbed by hair follicle and leaves the epidermis untouched.
The device comes with the wavelength between 400-1200nm and hair melanin absorption is higher at lower wavelength, making it challenging for the light to reach skin base, however higher wavelength reaches the skin base and more light energy is absorbed by hair follicle.
As the light energy is absorbed by hair follicle, it is converted into heat energy and damages cells of hair follicle. People often use cooling gels while going through the treatment to have cold and relaxing effect on the skin.