Yes it works and it is called phototherapy. Acne is caused by the inflammation of the oil gland as a result of blocked pores and bacterial infection. The bacteria responsible for acne can be killed by exposing the skin to blue light coming from an LED with a wavlength of 405nm-420nm. To hasten the healing of an infected oil gland, the skin is exposed to red light with a wavelength of 655nm-665nm ( Red ). The combination of blue and red light exposure helps in the reduction of pimple size and redness. Phototherapy study is published under the British Journal of Dermatology 142 (5), 973–978 and on the Mount Sinai School of Medicine under David Goldberg.