Publication brief – Photoprotection against visible light: Implications for clinical practice

Many sunscreens fail to protect against visible light (VL; 400-700nm), contributing to poor clinical outcomes and quality of life for individuals living with certain photodermatoses, according to a letter recently published in the journal of Photodermatology, Photoimmunology and Photomedicine.

The solar spectrum which penetrates the earth’s atmosphere consists of wavelengths of light from ultraviolet (UV; <400nm) through to infrared (>700nm) radiation, with around 43% consisting of VL. Sun Protection Factor (SPF) is the original unit for quantifying the level of protection in a particular sunscreen. However, it only accounts for UV-B wavelengths of light (280-315 nm) and is a measure of increase in burn time from exposure. As scientific knowledge of the impact of light has expanded, sunscreen manufacturers began to include a measure for UV-A (315-400 nm) protection as well. This is known as “broad spectrum” sunscreen.

More recently, harmful effects of VL have been discussed, including its role in DNA damage. Yet for some patients, visible light triggers acute symptoms of photodermatoses. These include patients with:

  • polymorphous light eruption,
  • hydroa vacciniforme,
  • actinic prurigo,
  • chronic actinic dermatitis,
  • cutaneous porphyrias and,
  • solar urticaria

The authors of the letter to editor, Searle et al. (2020), reference a particular case study of a patient experiencing solar urticaria caused by visible light.

A supporting article, in the Journal of the American Academy of Dermatology, remarks that for current sunscreens to protect against VL, they must be visible on the skin, which is why those using only nano particle inorganic filters which minimise the white-appearance on the skin, offer no VL protection.

By contrast, tinted sunscreens using varying concentrations of iron oxides and pigmentary (non-nano) titanium dioxide do provide protection against visible light. Both publications advocate the use of tinted, VL protecting, sunscreens for patients with visible light–induced photodermatoses, as well as a greater awareness in general of the effects of visible light on the skin.

For more details on photoprotection and the spectrum of photodermatoses, visit our webpage.

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