Visible light, falling within the wavelength range of 400 nm to 700 nm, is the portion of the electromagnetic spectrum that is perceived by the human eye, and is responsible for general illumination. It represents approximately 44% of all solar radiation, but is also emitted by anything that produces light: bulbs, televisions, computers, mobile phones, etc. at levels lower than the radiations of the solar spectrum.
Also known as high-energy visible light, blue light (400 to 500 nm) represents a specific wavelength of the visible white light spectrum. It has lower energy than UV radiation (280 to 400 nm) and can penetrate further into the dermis. Sunlight is thus the main source of blue light to which we are exposed, but fluorescent and LED bulbs, also emit it at levels lower than solar spectrum radiations.
Whilst it can be used for therapeutic purposes in the treatment of skin conditions (acne, psoriasis, precancerous lesions, atopic dermatitis, etc.), blue light could also induce direct and indirect negative effects on the skin. Indeed, recent studies show that blue light can trigger changes at the skin level and affect the complexion, even with short exposures. For several years now, visible light has thus become an additional factor in photoaging.
It would appear that the risk decreases beyond 500 nm.