Abstract and Introduction
Abstract
Sunscreens have been on the market for many decades as a means of protection against ultraviolet-induced erythema. Over the years, evidence has also shown their efficacy in the prevention of photoaging, dyspigmentation, DNA damage, and photocarcinogenesis. In the USA, most broad-spectrum sunscreens provide protection against ultraviolet B (UVB) radiation and short-wavelength ultraviolet A (UVA) radiation. Evidence suggests that visible light and infrared light may play a role in photoaging and should be considered when choosing a sunscreen. Currently, there is a paucity of US FDA-approved filters that provide protection against long UVA (> 370 nm) and none against visible light. Additionally, various sunscreen additives such as antioxidants and photolyases have also been reported to protect against and possibly reverse signs of photoaging. This literature review evaluates the utility of sunscreen in protecting against photoaging and further explores the requirements for an ideal sunscreen.
Introduction
Chronic sun exposure has long been known to cause photoaging, a process where the skin undergoes changes in epidermal thickness, increases in pigment heterogeneity and dermal elastosis, degradation of collagen in the dermis, development of ectatic vessels, and increases in mutagenesis of keratinocytes and melanocytes in the skin.[1] Clinically, this is characterized by an increase in rhytides, telangiectasias, dyspigmentation including lentigines and ephelides, volume loss, and cutaneous malignancies.[1] A recent observational study further characterized skin aging as hypertrophic and atrophic variants, with atrophic photoaging presenting with erythema and increased risk of skin cancers and hypertrophic photoaging with increased skin thickness and sallowness.[2]
In today's society, the value placed on a youthful appearance is reflected in the multibillion-dollar industry centered around anti-aging products.[3,4] It has been reported that approximately 80% of skin aging on the face can be attributed to ultraviolet (UV) exposure.[5] Therefore, despite the emphasis of the market on the reversal of skin aging, the best defense against cutaneous age-related changes is through prevention with rigorous photoprotection.[4] It should be noted that proper photoprotection consists of seeking shade when outdoors; wearing a wide-brimmed hat, photoprotective clothing, and sunglasses; and applying sun protection factor (SPF) ≥ 30 broad-spectrum tinted sunscreen on exposed sites.
In the USA, most broad-spectrum sunscreens provide protection against UVB radiation and short wavelength UVA radiation. However, there is a paucity of US FDA-approved filters that provide protection against long UVA (> 370 nm) and none against visible light (VL), making the ideal sunscreen a product that requires further innovation and research. Notable exceptions are pigmentary grade zinc oxide and titanium dioxide, which reflect VL; however, the whitish discoloration they leave on the surface of the skin makes them cosmetically unappealing to consumers. This review evaluates the utility of sunscreen in protecting against photoaging and further explores the requirements of an ideal sunscreen.
Am J Clin Dermatol. 2021;22(6):819-828. © 2021 Adis Springer International Publishing AG
