[interview] Top Concerns and New Directions for Sun/Skin Protection

There’s nothing like kicking off the summer season with fearmongering from a scathing review of what sunscreens U.S. consumers actually do have for skin protection. The Environmental Working Group (EWG) released its 18th Annual Guide to Sunscreens¹ on May 1, 2024, stating, “Just one in four sunscreens out of 1,700 SPF products assessed in EWG’s 2024 Guide to Sunscreens meets our standards for ingredient safety and sun protection efficacy.” With comments like this in the news, C&T reached out to experts to discuss market and formulation trends in this segment, in addition to misconceptions and future ideas. The following edited excerpts are from comments offered by Tomonobu Ezure, Ph.D. (TE), visiting professor of Kobe University, Kobe, Japan; and Howard Maibach, M.D. (HM), professor and dermatologist at University of California, San Francisco.

In response to the EWG, the Personal Care Products Council (PCPC) stated, “Unfortunately, once again, the [EWG’s] sunscreen guide misleads consumers into assuming sunscreen products are unsafe, thereby jeopardizing public health.”

More specifically, the EWG noted almost 300 products reviewed contained oxybenzone, octinoxate or both, and per EWG, “both ingredients have been shown to be harmful to human health and aquatic life.” While the scientific facts surrounding these claims are still debated,² the EWG also flagged half of the products in the guide for raising potential allergenic concerns, and almost 30% for listing fragrance on the label – which, per the EWG, “often refers to undisclosed mystery ingredients.” An additional concern included the lack of balanced UVA/UVB protection.

On the other hand, the most top-rated sunscreens identified by EWG contained zinc oxide and/or titanium dioxide, which the group states impart excellent sun protection with fewer health concerns. “Zinc oxide, for instance, provides stable protection from both UVA and UVB rays, offering broad-spectrum protection.” In the end, just 235 sunscreens were said to have met the EWG’s rigorous standards. "Products sold in the U.S. continue to fall short because of ongoing [U.S.] Food and Drug Administration (FDA) inaction,” EWG concluded.

While the PCPC criticized the EWG, reassuring its and industry’s commitment to ensuring that Americans have access to a wide variety of safe and effective sunscreen products, the council also acknowledged the need for new sunscreen active approvals in the U.S.

“…[W]e remain concerned that the Sunscreen Innovation Act, which was signed into law in 2014, has not lived up to its promise to increase the speed of approvals for new active sunscreen ingredients. The FDA has not approved new UV filters since 1999. Additionally, globally approved filters used in Europe and other regions are not available in the U.S., greatly limiting options for American consumers.” The council stated it will continue to work with the FDA to provide additional safety data on several ultraviolet (UV) filters in order to ensure consumer confidence in the safety and effectiveness of these critical products.

C&T: What are the biggest trends in sun/skin protection innovation?

TE: The basic UV protection ability of sunscreens has been drastically improved in recent years. In addition to this, the biggest innovation in sun protection products is better texture. Until recently, the texture of sunscreens was oily, to increase waterproofing. However, breakthroughs in emulsification have made it possible to get an aqueous texture with good water-resistance. This imparts a natural feeling suitable for daily use, as opposed to conventional oily sunscreen, which feels sticky and unnatural.

HM: The biggest trend was initiated by Dr. Matta at the FDA,³ who went to a contract research organization where tests were performed by applying sunscreen to most of the body and then looking for sunscreen actives either in blood or urine. What he learned was previously discovered but somewhat lost by us in the 1960s; namely: sunscreens stayed in the blood for longer than was predicted. He ended the article by stating the levels that were found. Was this a cause of concern for the agency? [Yes], considering that many people use sunscreens, some for the extent of their lives – especially athletes, who use it on large parts of their body – it is necessary to learn more by finding clever ways to understand the clinical implications of this for Homo sapiens.

A second trend, which was not possible until recently, is to try to find a way to administer sunscreens orally for their distribution to the entire skin surface. We now have a theoretical background to make this possible through something called percutaneous egression⁴ to get a chemical inside the body to the surface of skin. Interestingly, theoretically (not factually), this could make an oral sunscreen possible.

Another trend that we're beginning to understand a little bit more about is the science of adherence to the surface of skin when a product is applied externally⁵ – a term from the color industry known as substantivity. Obviously the more we understand about substantivity, the more effective the sunscreens we should be able to prepare.

C&T: What misconceptions are there when it comes to formulating sun/skin protection?

TE: Sunscreens used to be produced using a hydrophilic emulsifier in order to create a water-in-oil (w/o) type emulsion, but this has a sticky texture. However, the introduction of polymer emulsifiers enables the formation of oil-in-water (o/w) type emulsions that are resistant to water.

HM: I think the biggest problem is that we have not found a way to make it easy for the user to apply the proper amount of sunscreen. If you go to a department store, you’ll see the containers are really small. You won't find any one-gallon containers; that’s impractical. Most users don't apply enough sunscreen for it to be as effective as we would like, and that is a complex issue I don't think has been resolved yet – how to get them to use an amount that will be clinically effective.

C&T: What are today’s best solutions for effective sun/skin protection?

TE: Sun care products have focused on protecting skin against harmful UV light. However, one innovative technology⁶ based on fluorescent zinc oxide is making it possible to change toxic UV light to beneficial light to improve skin conditions – essentially, skin-beautifying light. This drastically changes the concept of sun protection by using sunlight in a positive way.

HM: The importance of UVA has lasted all these years. In terms of visible, infrared, etc., other parts of the UV light system, we have to get more data. I also applaud the science behind nanotechnology sunscreens but again, we need more data. When you get a new idea, you get a little bit of data but you want to see how it stands the test of time. And that doesn't happen instantly.

C&T: What are the biggest challenges to formulating sun/skin protection products?

TE: Non-chemical sunscreens, using UV filters without added UV absorbers, are attractive to consumers who are sensitive about given ingredients. However, UV filters leave a white cast on the skin. To overcome this, we need to understand the mechanism and the time-dependent change of the sunscreen on the skin. Some studies have already focused on this; e.g., the “Dynamic Homogenization of Inorganic UV Filters on the Skin for Enhanced UV Protection and Visual Transparency.”⁷

HM: Work at the FDA by Dr. Sam Raney is looking at how to quantify sensory experiences when using topical products, although with a different goal: trying to find ways to improve generic topical formulations without doing clinical trials, which are expensive. I think some of the science he is working on will eventually improve the user-friendliness of sunscreens.

C&T: How do regulations or testing constraints impact sun/skin protection product development?

TE: Sun care product launches focused on the negative influence of near infrared (NIR) have been increasing. NIR is generally reported as penetrating deeper into the skin, and may damage the dermal layer matrix, such as collagen and elastic fibers, due to its heating effect, though the influence of IR on the skin remains controversial. However, standard protocols and evaluation criteria have not yet been established, so product development is difficult.

HM: There are many more sunscreens commercially available in Europe than the United States. If you Google sunscreens USA vs. sunscreens Europe, you will find there many efforts to try to change U.S. sunscreen regulations, including attempts to try to influence Congress. In terms of why sunscreens are regulated as drugs and differently than cosmetics in the U.S., Peter Barton Hutt can explain⁸ the theoretical reasons, but it points to the wisdom of the FDA staff. For now, U.S. formulators basically have rules they obviously have to follow and they can’t go outside of the box. 

C&T: Should consumers and product developers truly be concerned about blue light exposure? What does the evidence suggest?

TE: Blue light is widely recognized as harmful, and many skin care products claim to protect against blue light. Increasing numbers of studies have found negative effects of blue light on skin cells, such as the disruption of collagen and elastic fibers, due to generation of reactive oxygen species.

HM: Some of the new publications you can find on Google by searching blue light suggest this concern may eventually be shown to be true and correct.

C&T: How might trending concepts such as anti-pollution, the microbiome, the mind-skin connection, etc., be leveraged in sun/skin protection?

TE: Sun protection can be one of the key factors to move forward to the next generation of anti-aging skin care. Many studies show that aged skin is more prone to damage by sunlight, both directly and indirectly, including the deterioration of the repair function of skin cells and chronic inflammation of aged skin or aged cells (senescent cells), leading to accelerated pigmentation. Thus, combinations of physical sun protection with sunscreen and a physiological approach to ameliorate skin aging may be the way forward.

HM: On these topics, you will find lots to quote on Google. The public practice as well as the scientific press are asking: What is the role of sunscreen? And the impact on coral reefs has certainly been a wakeup call. I guess the question goes back to whether these concepts might be something to integrate into your product development strategy. Sunscreens impacting coral reefs was not something we thought about 30 years ago but today it’s on a lot of people's minds. Skin microbiome is also in its very early days; it's just beginning.

C&T: What ideas or technologies could shape the future of sun/skin protection products?

TE: One key technology is aesthetic treatment devices. Various physical treatments for sun-damaged skin are used in the clinical field, such as laser, radio frequency (RF) and ultrasound. However, the mechanisms of their effects are not fully understood, and clarification of the mechanisms may provide important clues about how we can increase sun protection ability and treat sun damage with cosmetic products.

HM: I named a few, but of course synthetic chemistry and analytic chemistry have advanced enormously in your lifetime, so if there's a commercial incentive. People will go back to the drawing board to look for new sunscreens – what will hold them back are concerns relating to safety.

C&T: What is your take-away message to the industry about sun/skin protection?

TE: The quality and function of sun protection formulations has improved drastically in recent years. Progress in related fields, as I mentioned above, is also likely to contribute to advanced sun protection products. This could be one of the hottest fields in the cosmetic industry.

HM: I believe the forces you're talking about are influencing the management of the sunscreen companies. They have much more to think about than they did when we started in the 1940s – I guess that’s just a defense for how much more complex it's gotten, in terms of things to think about when you're developing products. And you never know when something else is going to pop up; either from serendipity or just specifically working on it.

References

1. EWG website. (Accessed 2024, May 7). EWG's 18th Annual Guide to Sunscreens. Available at https://www.ewg.org/sunscreen/report/executive-summary/

2. Grabenhofer, R. (2024, May 6). Walmart, Target flagged for 'deceptive' reef-friendly sunscreen claims. Cosmetics & Toiletries. Available at https://www.cosmeticsandtoiletries.com/regulations/eco-sustainable/news/22909119

3. Matta, M.K., Zusterzeel, R., ... Pilli, N.R., et al. (2019). Effect of sunscreen application under maximal use conditions on plasma concentration of sunscreen active ingredients. A randomized clinical trial. JAMA Network. Available at  https://jamanetwork.com/journals/jama/fullarticle/2733085

4. Sun, Q., Purvis, C.G., ... Maibach, H., et al. (2022). Percutaneous Egression: What do we know? Skin Pharmacology and Physiology. Karger. Available at https://karger.com/spp/article/35/4/187/826923/Percutaneous-Egression-What-Do-We-Know

5. Li, B.S., Cary, J.H. and Maibach, H.I. (2018, May 11). Stratum corneum substantivity: Drug development implications. Arch Derm Res. Available at https://pubmed.ncbi.nlm.nih.gov/29752541/

6. Shiseido. (2021, Nov 17). Shiseido develops innovative technology to convert ultraviolet light into light that brings about beneficial effects on the skin. Available at https://corp.shiseido.com/en/news/detail.html?n=00000000003256

7. IFSCC. (2023, Sep 20). Applied research award winner 2023. Available at https://ifscc.org/news/applied-research-award-winner-2023/

8. Hutt, P.B. (2005). Legal distinction in USA between cosmetic and drug. In: Elsner, P. and Maibach, H., eds., Cosmeceuticals and active cosmetics: Drugs versus cosmetics, p. 630, 2nd edn.