One research found that blue light, particularly in the wavelength range of 405–470 nm, can reduce acne-causing bacteria in 77% of cases after five weeks of diligent use. “Phototherapy using blue light source was effective and well-tolerated in acne patients and had an ability to decrease numbers of P. acnes by 64%,” suggests research. Similarly, a combination of blue-red lights has been reported to reduce inflammatory lesions from 69% up to 77%.