Sunless tanning and other developments in sun protection

Sunscreen use is an important means to prevent photodamage, yet data gaps still exist with regard to UV filters. Novel areas are sunless tanning and the prevention of damage by visible light.

As Dr Henry Lim (Henry Ford Health System, MI, USA) pointed out in his presentation, the FDA recognises only 2 UV filters –zinc oxide and titanium dioxide­– as generally safe [1]. For most of the other filters, insufficient safety data is available.

In an absorption study assessing 6 active ingredients, including oxybenzone and octinoxate, levels of >0.5 ng/ml in the blood and skin after single use were detected for all agents. Levels remained elevated longest with oxybenzone, until day 21. “But the results do not indicate that individuals should refrain from the use of sunscreens with UV filters; their use is still safe,” Dr Lim said. A review published last year analysed 29 studies on the impact of UV filters on human health. The study found that oxybenzone seems to have no adverse effect on male and female fertility, but associations were found of oxybenzone with thyroid hormone levels, testosterone level, kidney function, and pubertal timing that should be investigated further [2]. The authors concluded that current evidence is not sufficient to support the causal relationship between elevated systemic levels of oxybenzone or octinoxate and adverse health outcomes.

In a recently published article on the environmental impact of organic UV filter exposure, a risk was identified of oxybenzone and octinoxate above a certain concentration that might adversely impact corals. However major data gaps still need to be addressed [3]. Both agents were banned in Key West and Hawaii due to their toxic effects on marine ecosystems in January 2021.

Small molecules for sunless tanning appear to be an attractive novel concept for consumers. One example is afamelanotide, a potent alpha-melanocyte-stimulating hormone (αMSH) analogue, which stimulates the production of eumelanin in the skin. Subcutaneous implantation of afamelanotide is currently approved by the FDA for the treatment of erythropoietic protoporphyria; use as a self-tanning medication is off-label. Cyclic adenosine monophosphate inducers such as topical forskolin or salt-inducible kinase inhibitors are other interesting agents. However, all of them are still in the early stages of development [4].

A novel area in sun protection is the protection against visible light. Broad-spectrum sunscreens protect against ultraviolet radiation but do not adequately protect against visible light. Exposure to visible light can lead to melasma in people with dark skin and to erythema in those with light skin. “To protect against visible light, a sunscreen has to be tinted,” Prof. Lim explained. Tinted sunscreens use different formulations and concentrations of iron oxides and pigmentary titanium dioxide to provide protection against visible light. Many shades of tinted sunscreens are available by combining different amounts of iron oxides and pigmentary titanium dioxide to cater to all skin phototypes [5].

On how to advise our patients, Prof. Lim emphasised: “The practice of photoprotection is an entire package.” Patients should be advised to seek shade if possible and wear photoprotective clothing, a wide-brimmed hat, and sunglasses. In otherwise exposed areas people should apply SPF >30 broad-spectrum (to cover UVA), tinted (to cover visible light) sunscreen. Patients with concerns about the environmental effect of chemicals can use mineral sunscreens. Last but not least, patients who practise rigorous photoprotection should be recommended taking an oral supplement of vitamin D (600–800 IE daily).

1. Lim H. Sunscreens 2021. Session S027: Hot Topics. AAD VMX 2021, 23-25 April.
2. Suh S, et al. Int J Dermatol 2020;59:1033.
3. Matta K, et al. JAMA 2020:323 (3):256-67.
4. Mitchelmore CL, et al. Environmental Toxicology and Chemistry In press.
5. Rachmin I, et al. Adv Drug Deliv Rev 2020;153:65-71.

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Posted on 7 June 20217 June 2021