Sunscreens

Sunscreens have been on the market for many decades as a means of protection against ultraviolet-induced erythema (abnormal redness). Over the years, evidence has also shown their efficacy in the prevention of photoaging, dyspigmentation, DNA damage, and photocarcinogenesis (cancer caused by UV light).

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. Additionally, various sunscreen additives such as antioxidants and photolyases have also been reported to protect against and possibly reverse signs of photoaging.

In today’s society, the value placed on a youthful appearance is reflected in the multibillion-dollar industry centred around anti-aging products. It has been reported that approximately 80% of skin aging on the face can be attributed to ultraviolet (UV) exposure. Therefore, despite the emphasis of the market on the reversal of skin aging, the best defence against cutaneous age-related changes is through prevention with rigorous photoprotection. 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.

The concept of a topical photoprotective product has been around since the times of the ancient Egyptians in 4000 BC, but the first commercial sunscreens were not available until the 1920–1930s. At that time, understanding of UV radiation was limited and focused mainly on UVB protection. With the increasing popularity of sunscreen over the years, the concept of standardisation of photoprotection against UVB was introduced.

UV-induced erythema is mostly attributed to UVB, with a minor contribution by UVA2. The concept of SPF, an assessment using UV-induced erythema as an endpoint, as a sole measurement of sun protection persisted for many decades despite advances in the study of UVR suggesting that UVA may play a significant role in photoaging. In 1992, the UVA star rating system was created by The Boots Company in the UK but was not widely implemented. (Solar UV radiation (UVR) consists of UVA (320–400 nm), UVB (280–320 nm), and UVC (100–280 nm). UVA is further categorized as UVA1 (340–400 nm) and UVA2 (320–340 nm). UVC is the shortest wavelength and considered the most damaging type of UVR. However, it is completely absorbed by the ozone and does not reach the earth’s surface)

Sunscreen technology has made great advancements in accessibility, consumer acceptability, and overall safety and efficacy over the years. However, the challenges and limitations of current sunscreens leave room for further research and innovation.

Antioxidants play an important role in preventing, ameliorating, and dampening free radicals and oxidative stress. Although our bodies produce natural antioxidants, UVR and other stressors can often overwhelm our endogenous supply. Topical antioxidants have been formulated into sunscreens to replenish depleted antioxidant supplies and diminish oxidative stress on the skin. Yet the exact role and efficacy of antioxidants in sunscreens remains controversial. The variability in the efficacy of antioxidants in sunscreens may depend on the formulation of the sunscreen. It has been proposed that, for antioxidants to be efficacious, they must have high antioxidative capacities, be present in high concentrations, be stable in the final formulation, and be able to penetrate the stratum corneum and still exist at high enough concentrations in the epidermis and dermis to be effective.

In terms of antioxidants that have been explored in topical formulations, Vitamin C (l-ascorbic acid) is the predominant antioxidant in the skin and plays an important role in the skin’s aqueous compartments because of its water solubility. It also helps replenish Vitamin E, acts as a cofactor in collagen synthesis, and reduces elastin accumulation. It is not synthesized by the human body and must be replenished via oral intake. Additionally, because of its ionic charge at physiologic pH, it cannot penetrate the stratum corneum without becoming unstable. Fortunately, a stable formulation can be made by compounding it with other antioxidants: Vitamin E (Alpha-Tocopherol) and Ferulic Acid.

The perception of sunscreen use has shifted from purely protecting against UV-induced erythema to broad-spectrum protection against not only erythema but also photoaging, dyspigmentation, DNA damage, and photocarcinogenesis. The impact of visible light and IR light in photoaging is still being explored, but better methods of protection against these wavelengths are needed. Sunscreens continue to be adapted to provide the broadest coverage while being cosmetically appealing.

When choosing a sunscreen, a broad-spectrum tinted sunscreen with SPF ≥ 30 used daily will offer protection against UVR and VL to reduce their effects on photoaging. Additionally, sunscreen additives such as antioxidants, photolyases, and more have opened the door for not only improved photoprotection against but also the reversal of skin aging. However, larger-scale and replicable studies must be performed before clinical guidelines can be issued.

The above is taken from (not my own work) For more information, please read the full article.

Guan LL, Lim HW, Mohammad TF. Sunscreens and Photoaging: A Review of Current Literature. Am J Clin Dermatol. 2021 Nov;22(6):819-828. doi: 10.1007/s40257-021-00632-5. Epub 2021 Aug 13. PMID: 34387824; PMCID: PMC8361399.

Department of Dermatology, Henry Ford Health Systems, Henry Ford Medical Center-New Center One, 3031 W. Grand Boulevard, Suite 800, Detroit, MI 48202 USA