Should we protect ourselves against blue light?

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.

One of the established effects of blue light on the skin includes oxidative stress. Several studies have demonstrated that the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the skin can be rapidly stimulated during exposure to visible light. For instance, it has been shown that irradiating cultured human keratinocytes with 41.35 J/cm2 of blue light at a wavelength of 453 nm results in excessive generation of ROS and RNS after 1 hour. These unstable oxygen molecules can damage cellular structures such as DNA, lipids, and proteins. Indeed, when these molecular structures are damaged, it can contribute to the acceleration of the appearance of signs of skin ageing, such as wrinkles. Additionally, irradiating human skin in vivo with blue-violet light of 100 J/cm2 from 380 to 95 nm results in a significant decrease in skin carotenoids, antioxidants naturally present in the skin.

One of the most common skin impacts of exposure to blue light is thehyperpigmentation of the skin. The results are clear: blue light is capable of inducing both immediate and persistent pigmentation. A randomised, double-blind, placebo-controlled clinical study conducted by R. SCHUETZ on volunteers with phototypes IV to VI revealed that following repetitive irradiation with blue light (single peak at about 450 nm) for four consecutive days with 60 J/cm2 visible changes in the skin colour parameters were detected.

Researchers have even discovered that exposure to blue light results in more pronounced hyperpigmentation than that caused by UVA rays.

Indeed, a continuous increase in melanin levels following exposure to blue light has been observed. From a mechanistic perspective, it has been demonstrated that blue light would induce the deposition of melanin in skin explants. It has also been revealed that visible light ex vivo is capable of activating melanogenesis by inducing an increase in melanogenesis markers, such as tyrosinase and dopachrome tautomerase.

A study has established a link between exposure to blue light and increased swelling, redness, and pigmentation changes in individuals with darker skin. Indeed, exposure to blue light can increase the level of inflammation in skin cells. SOUTHALL M. D. and his team have demonstrated that visible light can induce the synthesis of pro-inflammatory cytokines, such as IL-1α, TNF-α, IL-8 and IL-6, and matrix metalloproteinases (MMP) 2 and 9 in human skin equivalents. However, the influence of blue light on inflammation is controversial as other studies have found no modulation of inflammatory markers in keratinocytes irradiated with blue light between 412 and 453 nm.

However, there are a few ways to protect oneself from the damage caused by the blue light.

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