PracticalDermatology

The new FDA proposed order limiting GRASE (generally recognized as safe and effective) sunscreen ingredients to zinc oxide and titanium dioxide has placed a spotlight on sunscreen efficacy and safety. Meanwhile, efficacious new ingredients developed by companies in Europe are now widely available outside of the US. It is important for US dermatologists to stay up to date on the latest sunscreen technology and data, since both social media and the resurgence of travel may cause patients to pose questions about these products.

Sunscreen Use and Vitamin D Levels

One potentially worrisome aspect of diligent sunscreen use could be the deleterious effect on endogenous vitamin D production. Vitamin D synthesis relies primarily on UVB exposure. UVA does not lead to vitamin D production, but in vitro evidence exists that exposure to UVA2 (315-340nm) may cause vitamin D degradation. Suberythema doses of UVB to a limited body surface area maintains a normal vitamin D level. An expert panel was convened to give recommendations on the association between sunscreen use and vitamin D levels.¹ Their conclusions are the following:

• Most studies show no association between recreational or daily sunscreen use and vitamin D deficiency, with some studies showing a positive correlation between sunscreen use and vitamin D3 levels.
• Increasing the UVA protection (which is not measured by SPF) reduces photodamage more than increasing the SPF; in fact, a high SPF inhibits sunburn, meaning that UV exposure can be prolonged with greater exposure to the more worrisome UVA damage. Therefore, increasing protection against UVA for any SPF will increase vitamin D production.
• People who are diligent with both highly protective sunscreen along with photoprotective clothing and shade-seeking behavior are truly prone to vitamin D deficiency.

Novel Sunscreen Ingredients

Currently approved sunscreen ingredients in the US protect against UVB, as well as UVA up to 370nm. UVA, however, extends to 400nm, and the World Health Organization classifies the entire UV spectrum (100-400nm) as carcinogenic. The development of new filters with absorption beyond 370nm, therefore, may offer enhanced protection to those currently available.

Mexoryl 400. Mexoryl 400 (Methoxypropylamino Cyclohexenylidene Ethoxyethylcyanoacetate or MCE) has a peak absorption at 385nm and has been approved in Europe for use up to 3% concentration.² In a randomized human trial, MCE was shown to reduce UVA1 induced pigmentation compared to a reference product protecting against UVB and UVA up to 370nm. Pigmentation analysis after UVA1 irradiation on the back skin of 19 volunteers showed that MCE 1.5% formula was significantly more successful than the reference product in reducing hyperpigmentation both at two and 24 hours after irradiation.

Genetic analysis was performed on fibroblasts in reconstructed skin models exposed to UVA1 in the presence of MCE 1.5% as well as a reference product. The MCE-containing formula significantly reduced the number of genes differentially expressed after UVA1 irradition, as well as reduced the amount of modulation of those genes that were expressed. These results were mirrored in the genetic analysis of keratinocytes in this study, as well.

Cell and tissue change analysis showed that the MCE formula (1.5%) completely protected from fibroblast disappearance after UVA1 exposure, which significantly differed from the reference product, which caused only partial attenuation of fibroblast death. This extended to protein expression analysis, with MCE formula reducing the release of inflammatory cytokines and matrix metalloproteinases, which was most evident when compared to the reference product at exposures of 60 and 80j/cm2.

TriAsorB. TriAsorB (phenylene bis-diphenyltriazine) was approved for use up to 5% by the European Scientific Committee on Consumer Safety in 2018.3 This filter offers protection to 450nm, well into the high-energy visible light (blue light) part of the visible UV spectrum. Blue light has been shown to have various effects on the epidermis and dermis, including causing barrier defects, having anti-proliferative and oxidative-stress effects, as well prolonged hyperpigmentation and inflammation.

Studies were performed on reconstructed human epidermis exposed to UV and visible light via a solar-simulated radiation. The use of TriAsorB reduced the formation of cyclobutane pyrimidine dimers (CPDs) by nearly 50 percent. In addition, TriAsorB reduced the level of formation of 80HdG, a biomarker of oxidative DNA damage that specifically appears upon blue light exposure.

Be Informed

Both Mexoryl 400 and TriAsorb are exciting additions to the portfolio of sunscreen ingredients and allow for truly broad-spectrum protection when ingredients are combined. While sunscreens in the US market are unlikely to contain these ingredients in the near to mid-term future, knowledge about them will help dermatologists to answer patient questions and make recommendations. In addition, recent data about use of sunscreen and vitamin D levels support daily application without the need for vitamin D supplementation except for the most careful patients.

Drs. Farris and Lain are co-founders of the Science of Skincare Summit, to be held October 28-30 in Austin, TX. For information: scienceofskincaresummit.com

1. Passeron, T., Bouillon, R., Callender, V., Cestari, T., Diepgen, T., Green, A., van der Pols, J., Bernard, B., Ly, F., Bernerd, F., Marrot, L., Nielsen, M., Verschoore, M., Jablonski, N. and Young, A. (2019), Sunscreen photoprotection and vitamin D status. Br J Dermatol, 181: 916-931.

2. Marionnet C, de Dormael R, Marat X, Roudot A, Gizard J, Planel E, Tornier C, Golebiewski C, Bastien P, Candau D, Bernerd F. Sunscreens with the New MCE Filter Cover the Whole UV Spectrum: Improved UVA1 Photoprotection In Vitro and in a Randomized Controlled Trial. JID Innov. 2021 Nov 25;2(1):100070.

3. Bacqueville, D., Jacques-Jamin, C., Dromigny, H. et al. Phenylene Bis-Diphenyltriazine (TriAsorB), a new sunfilter protecting the skin against both UVB + UVA and blue light radiations. Photochem Photobiol Sci 20, 1475–1486 (2021)