Work on the first sunscreen products began in the 1930s. Initially, such products were often unappealing in consistency and offered very low protection. It was not until the 1980s that the first products protecting against UVA and UVB radiation appeared on the market. Today, consumers can choose from a wide range of sunscreen products with broad spectrums of protection, not only against UV radiation, but also blue/visible light (VIS) and near-infrared A (IRA). The knowledge in this field is becoming more and more comprehensive, which sometimes means existing theories require revisiting and revising.1-6
With advances in the development of sunscreen products, it has become necessary to develop methods to accurately determine their effectiveness. Nowadays, two in vivo methods, ISO 24444: 2019 and FDA 2011, with complex protocols are available and widely used. While these methods should be used as references, in theory, preference should be given to in vitro test methods without volunteers since under the given circumstances, the methods are required to provide equivalent and reproducible results. Also, as in vivo methods may raise ethical concerns, increasing efforts to find sufficient replacements are justified. Currently, two alternative ISO methods are under validation and expected to be published in 2025.1-9
It would seem that the situation in SPF testing is promising, and that stable and safe sunscreens are being produced. But is this really so? Scientific evidence shows sunscreens are an effective way to reduce skin cancer risk but at the same time, the SPF world is facing the question: are sunscreens safe? In fact, nowadays, U.S. and European regulators are questioning the human health and environmental safety of 12 sunscreens filters.8-10
How does this affect both consumers and producers? An initial thought is: should the industry be concerned about presumptions that never gain the support of credible research? To answer these questions, it is first worth stepping back to review the roles and goals of sunscreens.
Sunscreen Product Success
By definition, per ISO 24444: 2019, sunscreen products are, "products containing any component able to absorb, reflect or scatter UV rays, which are intended to be placed on the surface of human skin with the purpose of protecting against erythema and other ultraviolet-induced damage.”8 As it is well-known, sunscreen products play an important role in protecting skin against the negative consequences of excessive exposure to UV radiation. In relation, the essential components of sunscreen products are UV filters. Such substances must fulfill certain requirements, such as efficacy at low concentrations and stability.
Penetration into the living layers of the epidermis is also undesirable, especially if products are designed for children or individuals with compromised skin. In most cases, physical (mineral) and chemical UV filters are combined in order to obtain broad-spectrum protection. Natural substances that can absorb UV radiation are also being introduced more frequently into formulations. Antioxidants, by neutralizing free radicals generated by UV, play an important role, additionally lowering the risk of skin damage.2-3, 9, 11-13
- Journal of the European Union (2006). Commission recommendations of September 22, 2006, on the effectiveness of sunscreen products and related them to statements (translated via Google; in Polish). Available at https://eur-lex.europa.eu/legal-content/PL/TXT/PDF/?uri=CELEX:32006H0647&from=PL
- Bojarowicz, H. and Bartnikowska, N. (2014). Sunscreen cosmetics. Part I. UV filters and their properties. Probl Hig Epidemiol 95(3) 596-601.
- Bojarowicz, H., Bartnikowska, N. (2014). Sunscreen cosmetics. Part II. Selection of optimum cosmetic product. Probl Hig Epidemiol 95(3) 602-608.
- Greelane (2019, Nov 23). So who invented sunscreen? Available at https://www.greelane.com/pl/humanistyka/historia-i-kultura/suncreen-history-1992440
- Banas, J. (2017, Jun 12). Sunbathing. A short history of skirmishes with the sun. Available at https://wyborcza.pl/alehistoria/7,121681,21929958,opalanie-krotka-historia-potyczek-ze-sloncem.html
- Pissavini, M. (2019) Effective sun protection: Do we need an SPF 100 or just an SPF 30 with excellent sensorial properties? Available at https://www.teknoscienze.com/Contents/Riviste/Sfogliatore/HPC3_2019/32/
- Pissavini, M., Tricaud, C. and Wiener, G. (2020). Validation of a new in vitro sun protection factor (SPF) method to include a wide range of sunscreen product emulsion types. Available at https://pubmed.ncbi.nlm.nih.gov/32390187/
- ISO (2019). ISO 24444: 2019 Cosmetics—Sun protection test methods—In vivo determination of the sun protection factor (SPF). Available at https://www.iso.org/standard/72250.html
- U.S. government (2011). Federal Register / Vol. 76, No. 117 / Friday, June 17, 2011 / Rules and Regulations. Available at https://www.govinfo.gov/content/pkg/FR-2011-06-17/pdf/2011-14771.pdf (accessed on Mar 4, 2022).
- FDA (2019, Feb 21). FDA advances new proposed regulation to make sure that sunscreens are safe and effective. Available at https://bit.ly/3pEskup
- Skin Cancer Foundation (accessed Mar 4, 2022). All about sunscreen. Why you need it. How it works for you. Available at https://www.skincancer.org/skin-cancer-prevention/sun-protection/sunscreen/
- U.S. government (2019, Feb 26). Sunscreen drug products for over-the-counter human use. Available at https://www.federalregister.gov/documents/2019/02/26/2019-03019/sunscreen-drug-products-for-over-the-counter-human-use
- Rawlings Parker, E. (2021, Jan). The influence of climate change on skin cancer incidence—A review of the evidence. Available at https://doi.org/10.1016/j.ijwd.2020.07.003