Abstract: A method of treating acne by illumination comprising the steps of utilizing at least one light emitting diode (LED) by driving each of the at least one LEDs in substantially continuous wave (CW) mode of operation to generate CW light radiation in a narrow bandwidth centered at a wavelength suitable for acne relief, concentrating and projecting the CW light radiation onto an acne-affected dermal zone for biostimulative treatment thereof and maintaining the light radiation for a prescribed treatment duration, wherein each of the at least one LEDs emits light of substantially the same wavelength and wherein the acne affected dermal zone is not simultaneously illuminated by stimulating radiation of another wavelength.