"Blue Light Acne Therapy," or "photodynamic therapy" as it's called, uses LED bulbs that emit light at a specific wavelength (415 nm) to kill the bacteria that cause acne to start and to persist and spread. Unlike a lot of other acne treatments, LED-based therapy is natural, painless and safe, and doesn't use harsh chemicals. Usually it involves just sitting in front of a blue-light emitting LED for a few minutes each day. It's common knowledge that the sun (or UV rays) help to fight acne, but it's also a well known fact that too much exposure to UV rays can damage skin or even cause skin cancer. In fact, light therapy for acne used to involve bathing beneath UV light rays until it was discovered that UV rays damage skin. Blue LEDs, however, are out of UV range, but still offer all of the benefits of UV therapy for troubled skin, without any of the dangerous side effects!
Blue light works by killing the acne-causing bacteria, P. acnes, and is most commonly used to treat inflammatory acne vulgaris that has not responded to other acne therapies. Several studies have documented to effectiveness of this treatment. For instance, a study published in the Journal of Cosmetic and Laser Therapy in June 2003 found that more than 80% of the patients treated with blue-light therapy responded to the treatment. The patients who responded saw a 59% to 67% reduction in inflammatory acne lesions.