Blue light, or high energy visible (HEV) light, is usually defined as light emitted by the sun in wavelengths ranging from 400–500 nm. Approximately 40% of the solar radiation reaching the earth’s surface is infrared light (> 800 nm), while 55% is visible light (400–800 nm) and ~7% is UV light (290–400 nm).
The damaging effects of UV on skin are well-studied and documented, as recent reviews illustrate. In particular, UV irradiation is considered the main contributor to skin photoaging, leading to fine lines, sagging and wrinkles, as well as thinning of the skin, hyperpigmentation and age spots. At a molecular level, these events are caused by: extracellular matrix degradation in the dermis, mainly of the collagen and elastic fibers; decreased cellular proliferation; and the disrupted regulation of pathways related to melanogenesis. These major cellular events result in DNA damage, inflammation, oxidative stress and apoptosis.