Sunscreens: Misconceptions and Misinformation

Over the past 70 years, sunscreens have evolved from beach products designed to prevent sunburn to more cosmetically elegant skincare products intended to protect against multiple long-term adverse consequences of characteristically low-intensity daily UV and visible light exposure. Sunscreen testing and labeling intended to quantify such protection are unfortunately often misunderstood by users and have also led to illegal misleading and potentially dangerous industry practices. Changes in regulatory requirements, better policing, and more informative sunscreen labeling would benefit users and their physician advisors. Over the past 70 years, sunscreens have evolved from beach products designed to prevent sunburn to more cosmetically elegant skincare products intended to protect against multiple long-term adverse consequences of characteristically low-intensity daily UV and visible light exposure. Sunscreen testing and labeling intended to quantify such protection are unfortunately often misunderstood by users and have also led to illegal misleading and potentially dangerous industry practices. Changes in regulatory requirements, better policing, and more informative sunscreen labeling would benefit users and their physician advisors. Sunscreens were first commercialized in the 1950s by Franz Greiter and colleagues as a means of preventing sunburn among fair-skinned Europeans and Americans (Pathak et al., 1983Pathak M.A. Fitzpatrick T.B. Parrish J.A. Topical and systemic approaches to protection of human skin against harmful effects of solar radiation.in: Regan J.D. Parrish J.A. The science of photomedicine. Springer, New York City, NY1983: 441-473Google Scholar). He coined the term sun protection factor or sun-protection factor (SPF) as a short-hand measure of this protection, defined as the sun exposure time for sunscreen-protected skin to develop delayed erythema divided by that of unprotected skin (Pathak et al., 1983Pathak M.A. Fitzpatrick T.B. Parrish J.A. Topical and systemic approaches to protection of human skin against harmful effects of solar radiation.in: Regan J.D. Parrish J.A. The science of photomedicine. Springer, New York City, NY1983: 441-473Google Scholar). Thus, someone who would typically develop a mild sunburn 16−24 hours after a 30-minute exposure, when using an SPF 10 sunscreen would develop an equivalent sunburn after a 300-minute or 5-hour exposure. Expressed differently, an SPF 10 sunscreen transmits to the skin 1/SPF or 1/10 (10%) of the energy responsible for sunburn. A product’s SPF is determined by exposing small squares on a test subject’s back, half of them after application of the product, to increasing doses of natural sunlight or solar-simulated laboratory-generated light and then examining the area the following day (Pathak et al., 1983Pathak M.A. Fitzpatrick T.B. Parrish J.A. Topical and systemic approaches to protection of human skin against harmful effects of solar radiation.in: Regan J.D. Parrish J.A. The science of photomedicine. Springer, New York City, NY1983: 441-473Google Scholar). Unfortunately, this method is well-documented to yield variable SPF values, depending on the test subjects’ skin type and other variables (Andrews et al., 2022Andrews D.Q. Rauhe K. Burns C. Spilman E. Temkin A.M. Perrone-Gray S. et al.Laboratory testing of sunscreens on the US market finds lower in vitro SPF values than on labels and even less UVA protection.Photodermatol Photoimmunol Photomed. 2022; 38: 224-232Crossref PubMed Scopus (6) Google Scholar; Ricci et al., 2020Ricci T. Marra A. Rauen K. Caswell M. Bias in sunscreen SPF testing: a review of published data.J Cosmet Sci. 2020; 71: 351-360PubMed Google Scholar; Wang and Lim, 2011Wang S.Q. Lim H.W. Current status of the sunscreen regulation in the United States: 2011 Food and Drug Administration's final rule on labeling and effectiveness testing.J Am Acad Dermatol. 2011; 65: 863-869Abstract Full Text Full Text PDF PubMed Scopus (74) Google Scholar), as made clear from the wide range of UV absorption profiles for selected commercial sunscreens labeled as having SPF values of 30–70 (Figure 1a ). This SPF is often found to differ from that deduced by the subsequently developed in vitro method determining the transmission of solar-simulated UVB (290–320 nm) through a standardized amount of sunscreen product in a laboratory setting (Ricci et al., 2020Ricci T. Marra A. Rauen K. Caswell M. Bias in sunscreen SPF testing: a review of published data.J Cosmet Sci. 2020; 71: 351-360PubMed Google Scholar). Nevertheless, the Food and Drug Administration (FDA) and equivalent agencies in Europe and Asia still require in vivo SPF determination and a value of at least 15 before a sunscreen is labeled and sold (Wang and Lim, 2011Wang S.Q. Lim H.W. Current status of the sunscreen regulation in the United States: 2011 Food and Drug Administration's final rule on labeling and effectiveness testing.J Am Acad Dermatol. 2011; 65: 863-869Abstract Full Text Full Text PDF PubMed Scopus (74) Google Scholar). By the 1990s, it had also been well-established that UVB irradiation caused skin cancers in mice (Kligman et al., 1980Kligman L.H. Akin F.J. Kligman A.M. Sunscreens prevent ultraviolet photocarcinogenesis.J Am Acad Dermatol. 1980; 3: 30-35Abstract Full Text PDF PubMed Scopus (169) Google Scholar) and that DNA mutations in humans mechanistically related to skin cancers, such as those inactivating the p53 tumor suppressor protein (Brash et al., 1991Brash D.E. Rudolph J.A. Simon J.A. Lin A. McKenna G.J. Baden H.P. et al.A role for sunlight in skin cancer: UV-induced p53 mutations in squamous cell carcinoma.Proc Natl Acad Sci USA. 1991; 88: 10124-10128Crossref PubMed Scopus (1792) Google Scholar). Furthermore, regular UVB-protective sunscreen use was shown to reduce the incidence of both squamous cell carcinomas (van der Pols et al., 2006van der Pols J.C. Williams G.M. Pandeya N. Logan V. Green A.C. Prolonged prevention of squamous cell carcinoma of the skin by regular sunscreen use.Cancer Epidemiol Biomarkers Prev. 2006; 15: 2546-2548Crossref PubMed Scopus (332) Google Scholar) and melanomas (Green et al., 2011Green A.C. Williams G.M. Logan V. Strutton G.M. Reduced melanoma after regular sunscreen use: randomized trial follow-up.J Clin Oncol. 2011; 29: 257-263Crossref PubMed Scopus (590) Google Scholar) in a well-controlled long-term prospective Australian study of human volunteers. In contrast to the human sunburn studies, the precise action spectrum for human photocarcinogenesis could not be determined, leaving open the possibility that longer and more deeply penetrating wavelengths (UVA, 320−400 nm) contribute. Because UVA penetrates far more deeply into the skin than UVB (Pathak et al., 1983Pathak M.A. Fitzpatrick T.B. Parrish J.A. Topical and systemic approaches to protection of human skin against harmful effects of solar radiation.in: Regan J.D. Parrish J.A. The science of photomedicine. Springer, New York City, NY1983: 441-473Google Scholar), it was also deemed likely to be substantially responsible for so-called photoaging, the wrinkling, dyspigmentation, and other changes that characterize habitually sun-exposed skin of older adults. Over time, clinical observations and animal experiments (Kligman et al., 1996Kligman L.H. Agin P.P. Sayre R.M. Broad-spectrum sunscreens with UVA I and UVA II absorbers provide increased protection against solar-simulating radiation-induced dermal damage in hairless mice.J Soc Cosmet Chem. 1996; 47: 129-155Google Scholar) provided compelling support for the belief that even the longest and least energetic wavelengths of the UV spectrum (UVA I, 340−400 nm) as well as visible light (400−700 nm) contribute to this damage as well as to melasma and other pigmentary disorders (Boukari et al., 2015Boukari F. Jourdan E. Fontas E. Montaudié H. Castela E. Lacour J.P. et al.Prevention of melasma relapses with sunscreen combining protection against UV and short wavelengths of visible light: a prospective randomized comparative trial.J Am Acad Dermatol. 2015; 72: 189-190.e1Abstract Full Text Full Text PDF PubMed Scopus (123) Google Scholar; Kohli et al., 2018Kohli I. Chaowattanapanit S. Mohammad T.F. Nicholson C.L. Fatima S. Jacobsen G. et al.Synergistic effects of long-wavelength ultraviolet A1 and visible light on pigmentation and erythema.Br J Dermatol. 2018; 178: 1173-1180Crossref PubMed Scopus (82) Google Scholar; Kullavanijaya and Lim, 2005Kullavanijaya P. Lim H.W. Photoprotection.J Am Acad Dermatol. 2005; 52 (quiz 59–62): 937-958Abstract Full Text Full Text PDF PubMed Scopus (358) Google Scholar; Mahmoud et al., 2010Mahmoud B.H. Ruvolo E. Hexsel C.L. Liu Y. Owen M.R. Kollias N. et al.Impact of long-wavelength UVA and visible light on melanocompetent skin.J Invest Dermatol. 2010; 130: 2092-2097Abstract Full Text Full Text PDF PubMed Scopus (262) Google Scholar; Martini and Maia Campos, 2018Martini A.P.M. Maia Campos P.M.B.G. Influence of visible light on cutaneous hyperchromias: clinical efficacy of broad-spectrum sunscreens.Photodermatol Photoimmunol Photomed. 2018; 34: 241-248Crossref PubMed Scopus (31) Google Scholar) that preferentially affect younger adults with darker skin types. Unfortunately, the precise action spectra for all these endpoints, requiring months to decades of sun exposure, is and likely will remain unknown. Thus, no measure equivalent to the SPF for sunburn prevention can be devised. Instead, the concept of broad-spectrum protection was developed, and sunscreen formulas were modified to scatter or absorb wavelengths beyond the UVB range responsible for sunburn into at least the UVA range (Wang and Lim, 2011Wang S.Q. Lim H.W. Current status of the sunscreen regulation in the United States: 2011 Food and Drug Administration's final rule on labeling and effectiveness testing.J Am Acad Dermatol. 2011; 65: 863-869Abstract Full Text Full Text PDF PubMed Scopus (74) Google Scholar). Ambient sunlight comprises approximately 0.5% UVB, 5% UVA, 45% visible light, and 50% infrared (heat) energy (Pathak et al., 1983Pathak M.A. Fitzpatrick T.B. Parrish J.A. Topical and systemic approaches to protection of human skin against harmful effects of solar radiation.in: Regan J.D. Parrish J.A. The science of photomedicine. Springer, New York City, NY1983: 441-473Google Scholar), although the specific amount of energy in each waveband varies with season, location of the earth’s surface, time of day, cloud cover, and other variables. Because UVA, unlike UVB, is relatively abundant in sunlight all day and all year and is also substantially transmitted through standard window glass (Pathak et al., 1983Pathak M.A. Fitzpatrick T.B. Parrish J.A. Topical and systemic approaches to protection of human skin against harmful effects of solar radiation.in: Regan J.D. Parrish J.A. The science of photomedicine. Springer, New York City, NY1983: 441-473Google Scholar), the market for sunscreens gradually expanded from beach products to a cornerstone of year-round daily skin care for many consumers. The resulting demand for such sunscreens led to parallel efforts on the part of sunscreen manufacturers to satisfy this demand. In recent years, the focus on appropriate photoprotection has shifted to emphasize the relatively modest role of visible light in cutaneous photodamage, particularly its role in melasma and other hyperpigmentation disorders (Boukari et al., 2015Boukari F. Jourdan E. Fontas E. Montaudié H. Castela E. Lacour J.P. et al.Prevention of melasma relapses with sunscreen combining protection against UV and short wavelengths of visible light: a prospective randomized comparative trial.J Am Acad Dermatol. 2015; 72: 189-190.e1Abstract Full Text Full Text PDF PubMed Scopus (123) Google Scholar; Kohli et al., 2018Kohli I. Chaowattanapanit S. Mohammad T.F. Nicholson C.L. Fatima S. Jacobsen G. et al.Synergistic effects of long-wavelength ultraviolet A1 and visible light on pigmentation and erythema.Br J Dermatol. 2018; 178: 1173-1180Crossref PubMed Scopus (82) Google Scholar; Mahmoud et al., 2010Mahmoud B.H. Ruvolo E. Hexsel C.L. Liu Y. Owen M.R. Kollias N. et al.Impact of long-wavelength UVA and visible light on melanocompetent skin.J Invest Dermatol. 2010; 130: 2092-2097Abstract Full Text Full Text PDF PubMed Scopus (262) Google Scholar; Martini and Maia Campos, 2018Martini A.P.M. Maia Campos P.M.B.G. Influence of visible light on cutaneous hyperchromias: clinical efficacy of broad-spectrum sunscreens.Photodermatol Photoimmunol Photomed. 2018; 34: 241-248Crossref PubMed Scopus (31) Google Scholar). This emphasis has provided the sunscreen industry with a welcome new story and an expanded market of darker-skinned individuals unconcerned by sunburn risk or even photoaging but prone to unwanted hyperpigmentation. The emphasis on visible light protection also deflects attention from the technical difficulty of providing truly broad-spectrum UVA-blocking products that rely on existing UV filters. Instead, tints, red, yellow, and/or black iron oxides in varying amounts are added to sunscreen formulas to provide substantial absorption throughout the UVA I and visible light spectra (Lyons et al., 2021Lyons A.B. Trullas C. Kohli I. Hamzavi I.H. Lim H.W. Photoprotection beyond ultraviolet radiation: a review of tinted sunscreens.J Am Acad Dermatol. 2021; 84: 1393-1397Abstract Full Text Full Text PDF PubMed Scopus (81) Google Scholar). By varying the amounts of different colored iron oxides and nonmicronized titanium dioxide, which appears white on the skin, the manufacturer can create colored makeup-like sunscreen products intended to match a user’s skin color (Lyons et al., 2021Lyons A.B. Trullas C. Kohli I. Hamzavi I.H. Lim H.W. Photoprotection beyond ultraviolet radiation: a review of tinted sunscreens.J Am Acad Dermatol. 2021; 84: 1393-1397Abstract Full Text Full Text PDF PubMed Scopus (81) Google Scholar). It is anticipated that tinted sunscreens may best find acceptance among users afflicted with symptomatic visible light−induced dermatoses, such as porphyria or solar urticaria (Austin et al., 2021Austin E. Geisler A.N. Nguyen J. Kohli I. Hamzavi I. Lim H.W. et al.Visible light. Part I: Properties and cutaneous effects of visible light.J Am Acad Dermatol. 2021; 84: 1219-1231Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar), whereas those with more subtle problems attributable in unknown part to visible light may instead wish to rely on more cosmetically elegant broad-spectrum UVA I protection that offers modest extension into the visible light spectrum. Some recent sunscreen innovations and points of advertising emphasis have generated areas of confusion, misinformation, and questionable safety of some products for both the user and the environment. We present below data generated using standard FDA-mandated testing methods and commercially available sunscreens to highlight and clarify these issues. Finally, we suggest changes in sunscreen ingredients and product labeling that might reduce current confusion and guide consumers to sunscreens that best address their specific concerns. Although the FDA-mandated descriptor Broad Spectrum suggests to sunscreen users minimal transmission of wavelengths across the UV spectrum, this is often not the case (Figure 1a). The current FDA definition of broad spectrum requires only an SPF rating of at least 15 and that the wavelength cutoff for 90% of the total UV energy (290−400 nm) blocked by the product be at or beyond 370 nm3 (Figure 1a). The choice of a 370 nm critical wavelength cutoff, in the absence of action spectra for long-term adverse UVA effects, is arbitrary and seemingly based primarily on the efficacy profiles of currently marketed sunscreens. Ironically, the definition also encourages lower UVB protection levels, although the in vivo SPF determination on the product label often conceals this from the user. Such labeling is minimally informative, especially if the user’s goal is to prevent unwanted consequences of sun exposure such as melasma or lentigines. Moreover, the definition results in nonsensical exclusions for the broad-spectrum designation (Figure 1a). SPF determinations, as required by the FDA, are performed with a specified amount of sunscreen: 1.3 mg/cm2 for in vitro determinations and 2 mg/cm2 for in vivo determinations (Kullavanijaya and Lim, 2005Kullavanijaya P. Lim H.W. Photoprotection.J Am Acad Dermatol. 2005; 52 (quiz 59–62): 937-958Abstract Full Text Full Text PDF PubMed Scopus (358) Google Scholar). However, studies have documented that test subjects, when instructed to apply sunscreen in their customary manner, apply far less (closer to 0.5−0.8 mg/cm2) than the FDA-specified amount for determination of the SPF rating in vivo (Kullavanijaya and Lim, 2005Kullavanijaya P. Lim H.W. Photoprotection.J Am Acad Dermatol. 2005; 52 (quiz 59–62): 937-958Abstract Full Text Full Text PDF PubMed Scopus (358) Google Scholar). This greatly increases the amount of both UVB and UVA energy transmitted through the product to the skin (Figure 1b and c). Given the high SPF values for many sunscreens, such under protection may not result in sunburn, but cumulative effects of years-long less-than-expected protection across the entire UV and visible spectra are however difficult to assess. Sunscreen-active ingredients are classified as chemical or mineral (also termed organic or inorganic). Chemical ingredients, such as avobenzone, contain aromatic ring structures and absorb UV energy, characteristically in the UVB range, although some also have an absorption shoulder in the UVA range (Pathak et al., 1983Pathak M.A. Fitzpatrick T.B. Parrish J.A. Topical and systemic approaches to protection of human skin against harmful effects of solar radiation.in: Regan J.D. Parrish J.A. The science of photomedicine. Springer, New York City, NY1983: 441-473Google Scholar). Absorption of photons randomly causes these molecules to decompose and lose their ability to further absorb UV energy. Because they do not absorb visible light, however, they are invisible on the skin and thus considered cosmetically elegant. Mineral sunscreen ingredients, such as the commonly used zinc oxide or titanium dioxide, scatter wavelengths across the entire UV (290−400 nm) and visible (400−700 nm) spectra. They may also absorb light of certain wavelengths depending on their bandgaps, which are in turn determined by their particle sizes (Cheng et al., 2006Cheng H.-M. Lin K.-F. Hsu H. Hsieh W. Size dependence of photoluminescence and resonant Raman scattering from ZnO quantum dots.Appl Phys Lett. 2006; 88261909Crossref PubMed Scopus (163) Google Scholar). They are chemically inert and photostable. Unfortunately, the degree of protection depends on the amount applied, as it does for all sunscreens, and at higher amounts of conventional preparations, the scattering of visible light gives a white cast to the skin that is considered a cosmetic liability by most users. Fortunately, scattering of light by particles is size dependent (Plass, 1966Plass G.N. Mie scattering and absorption cross sections for absorbing particles.Appl Opt. 1966; 5: 279-285Crossref PubMed Scopus (44) Google Scholar). Modifications will be required in the manufacturing process for zinc oxide to produce smaller particles that retain the ability to reflect incident light while remaining invisible on the skin surface even at moderately high concentrations. Concerns regarding the traditionally more transparent chemical sunscreens thus include their photolabilty, usually requiring reapplication over the course of the day to maintain the advertised degree of protection. In addition, it is now well-documented that chemical sunscreen ingredients can cause irritant or allergic contact dermatitis (Schauder and Ippen, 1997Schauder S. Ippen H. Contact and photocontact sensitivity to sunscreens. Review of a 15-year experience and of the literature.Contact Dermatitis. 1997; 37: 221-232Crossref PubMed Scopus (244) Google Scholar) and are absorbed through users’ skin (Matta et al., 2020Matta M.K. Florian J. Zusterzeel R. Pilli N.R. Patel V. Volpe D.A. et al.Effect of sunscreen application on plasma concentration of sunscreen active ingredients: a randomized clinical trial.JAMA. 2020; 323 ([published correction appears in JAMA 2020;323:1098]): 256-267Crossref PubMed Scopus (143) Google Scholar) and can be detected in blood and breast milk (Krause et al., 2012Krause M. Klit A. Blomberg Jensen M. Søeborg T. Frederiksen H. Schlumpf M. et al.Sunscreens: are they beneficial for health? An overview of endocrine disrupting properties of UV-filters.Int J Androl. 2012; 35: 424-436Crossref PubMed Scopus (348) Google Scholar), raising concerns about endocrine disruption (Schneider and Lim, 2019Schneider S.L. Lim H.W. Review of environmental effects of oxybenzone and other sunscreen active ingredients.J Am Acad Dermatol. 2019; 80: 266-271Abstract Full Text Full Text PDF PubMed Scopus (199) Google Scholar) and other adverse effects with regular long-term use. Adverse environmental effects, such as damage to coral (Ouchene et al., 2019Ouchene L. Litvinov I.V. Netchiporouk E. Hawaii and other jurisdictions ban oxybenzone or octinoxate sunscreens based on the confirmed adverse environmental effects of sunscreen ingredients on aquatic environments.J Cutan Med Surg. 2019; 23: 648-649Crossref PubMed Scopus (31) Google Scholar; Schneider and Lim, 2019Schneider S.L. Lim H.W. Review of environmental effects of oxybenzone and other sunscreen active ingredients.J Am Acad Dermatol. 2019; 80: 266-271Abstract Full Text Full Text PDF PubMed Scopus (199) Google Scholar), are also of concern and have led Hawaii, Key West, and the U.S. Virgin Islands, for example, to prohibit the sale or use of all chemical sunscreens (Fivenson et al., 2020Fivenson D. Sabzevari N. Qiblawi S. Blitz J. Norton B.B. Norton S.A. Sunscreens: UV filters to protect us: part 2-Increasing awareness of UV filters and their potential toxicities to us and our environment.Int J Womens Dermatol. 2020; 7: 45-69Crossref PubMed Scopus (52) Google Scholar). Without ultramicronized zinc oxide or titanium dioxide particles, consumers are left with a dilemma: to use a chemical sunscreen product potentially harmful to users and the environment or a mineral sunscreen that typically leaves a white cast and tends to feel greasy on the skin. For users content with a makeup-like sunscreen, a solution to this problem is the addition of a skin-tone pigment to a mineral sunscreen that masks the white cast (Austin et al., 2021Austin E. Geisler A.N. Nguyen J. Kohli I. Hamzavi I. Lim H.W. et al.Visible light. Part I: Properties and cutaneous effects of visible light.J Am Acad Dermatol. 2021; 84: 1219-1231Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar), although users tend to apply far less than recommended, decreasing protection. Some sunscreen manufacturers appear to have chosen the less straightforward solution of doping, defined as the addition of a non-FDA−approved UV filter described on the label as a stabilizer to a product described on the label as a mineral sunscreen. This component then increases the mineral sunscreen product’s UVB and UVA II absorption without requiring a concentration of mineral UV filters sufficient to produce the unwanted white cast. In other cases, such an ingredient is added as a stabilizer to a known chemical sunscreen to boost its UVB and UVA II absorption without exceeding the maximum-permitted concentration of its known, approved chemical sunscreen ingredient(s). See Table 1 for an analysis of the products shown in Figure 1.Table 1Both Chemical- and Mineral-Labeled Sunscreens Are Frequently Doped, Impairing the Ability of Consumers and Regulators to Identify Products with Medical or Environmental Concerns and Enhancing the Labeled SPF Using Non-FDA−Approved Chemical FiltersBrandSunscreen NameLabeled TypeDoped?Likely Doping Ingredient(s)SkinBetter ScienceSunbetter Sheer SPF 70MineralYesButyloctyl salicylateNeutrogenaUltrasheet Dry-touch Sunscreen SPF 55ChemicalYesButyloctyl salicylateISDINPhoto Eryfotona Actinica Ultralight Emulsion SPF 50+MineralNoTatchaSilk Sunscreen SPF 50MineralYesTridecyl salicylateLa Roche PosayAnthelios Light Fluid Sunscreen SPF 50MineralYesButyloctyl salicylate, Diethylhexyl syringylidenemalonateLa Roche PosayAnthelios Mineral Sunscreen Gentle Lotion SPF 50MineralYesDiethylhexyl syringylidenemalonate, Capryloyl salicylic acidEltaMDUV Clear SPF 46HybridNoEltaMDUV Daily SPF 40HybridNoSupergoopUnseen Sunscreen SPF 40ChemicalNoSkinMedicaEssential Defense Mineral Shield Broad Spectrum SPF 35MineralNoSummer FridaysShade Drops Sunscreen SPF 30MineralYesEthyl ferulateLa Roch PosayAnthelios HA Mineral SPF 30MineralYesDiethylhexyl syringylidenemalonate, Capryloyl salicylic acidSupergoopMineral Sheerscreen SPF 30MineralYesButyloctyl salicylateAbbreviations: FDA, Food and Drug Administration; SPF, sun-protection factor.Products are identified as doped (column 4) if they contain one or more ingredients listed on the product label as a stabilizer but are known to contain a ring structure capable of absorbing UV light and/or being highly similar to known chemical UV filters. In some cases, sunscreen manufacturing literature provides UV absorption profiles for such stabilizers. Open table in a new tab Abbreviations: FDA, Food and Drug Administration; SPF, sun-protection factor. Products are identified as doped (column 4) if they contain one or more ingredients listed on the product label as a stabilizer but are known to contain a ring structure capable of absorbing UV light and/or being highly similar to known chemical UV filters. In some cases, sunscreen manufacturing literature provides UV absorption profiles for such stabilizers. The precise composition of all commercial sunscreens remains a trade secret. To address the possibility that a suspected doping ingredient listed on the mineral sunscreen label contributes to the product’s listed UVB and UVA II absorption, we performed the following experiments. The suspected doping sunscreen ingredient at 5%, the same concentration specified on the label of the marketed mineral sunscreen as a stabilizer, was prepared in our laboratory in a standard sunscreen base lacking other UV filters and compared with the same base composition lacking the stabilizer. Unsurprisingly, the tested stabilizers absorb UVB and UVA II (Figure 2a). Butyloctyl salicylate is in the same salicylate family as FDA-approved chemical UV filters homosalate and octisalate, and ethyl ferulate is an analog of the FDA-approved chemical UV filter octinoxate (Figure 2b). Also unsurprisingly, in vitro studies documented skin penetration of these doping ingredients (Figure 2c), using the same standard methodology as used in studies that gave rise to human health concerns about the absorption of chemical sunscreen ingredients (Matta et al., 2020Matta M.K. Florian J. Zusterzeel R. Pilli N.R. Patel V. Volpe D.A. et al.Effect of sunscreen application on plasma concentration of sunscreen active ingredients: a randomized clinical trial.JAMA. 2020; 323 ([published correction appears in JAMA 2020;323:1098]): 256-267Crossref PubMed Scopus (143) Google Scholar). These results suggest that sunscreen users concerned about possible adverse effects of chemical filters on their health and/or on the environment may wish to avoid inaccurately labeled mineral sunscreens as well as chemical sunscreens with prohibited levels of chemical filters. Equally, regulatory agencies might require that all known or reasonably presumed chemical filters be so identified in product labels or omitted if shown to be acting as non-FDA−approved chemical UV filters. Numerous concerns have been raised regarding the FDA-mandated sunscreen rating system. These include the often misleadingly high in vivo SPF designations (Andrews et al., 2022Andrews D.Q. Rauhe K. Burns C. Spilman E. Temkin A.M. Perrone-Gray S. et al.Laboratory testing of sunscreens on the US market finds lower in vitro SPF values than on labels and even less UVA protection.Photodermatol Photoimmunol Photomed. 2022; 38: 224-232Crossref PubMed Scopus (6) Google Scholar) and the poorly understood and arbitrary broad-spectrum designation that provides very little guidance to consumers on the degree of UVA protection. These shortcomings are compounded by the fact that the current SPF rating system suggests to consumers misleadingly large differences, for example, among products blocking 99% of erythemogenically weighted UVB (SPF 100), 98% of erythemogenically weighted UVB (SPF 50), 97% of erythemogenically weighted UVB (SPF 30), or 95% of erythemogenically weighted UVB (SPF 20), especially considering that the customarily applied amounts of sunscreen do not achieve the labeled degree of protection in any case. For example, SPF ratings for the UVB portion of the spectrum might better be given as the percentage of erythemogenic energy blocked, that is, as SPF 95 rather than as the present SPF 20 or, better, the somewhat lower value obtained when the tested film is 0.5 mg/cm2 rather than the currently mandated 1.3 mg/cm2 (Figure 1). Meaningful UVA protection ratings are far more difficult to construct, given that the action spectra for the multiple delayed adverse effects are unknown and may well involve interactions among different portions of the UV spectrum, including UVB. New labeling should eliminate or at least sideline the present rather meaningless SPF wars and allow consumers to differentiate between high and low levels of UVA and visible light protection as well as UVB protection in marketed products. At present, perhaps labels should simply provide a diagram showing the proportion of UV energy blocked by the sunscreen (Figure 1) over a shaded area showing the range of other products’ protection. Concerned users or their advising physicians could then select or recommend specific sunscreens, on the basis of specific goals for short-term and long-term sun protection. As future research clarifies the action spectra for photoaging, melasma, and other as yet poorly understood adverse effects of chronic sun exposure, the rating system could be modified to convey the new information. Finally, because the issue of vitamin D sufficiency has been repeatedly raised in debates over sunscreen usage, it should be emphasized that the action spectrum for cutaneous vitamin D production is well-established and solidly in the UVB range (Wolpowitz and Gilchrest, 2006Wolpowitz D. Gilchrest B.A. The vitamin D questions: how much do you need and how should you get it?.J Am Acad Dematol. 2006; 54: 301-317Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar). Population studies have shown that regular use of high SPF sunscreens is not associated with vitamin D deficiency, likely because maximal vitamin D synthesis requires little UVB exposure and/or because sufficient vitamin D is obtained from a typical American or European diet (Reddy and Gilchrest, 2010Reddy K.K. Gilchrest B.A. What is all this commotion about vitamin D?.J Invest Dermatol. 2010; 130: 321-326Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar). Hence, regular use of a true broad-spectrum sunscreen would similarly pose no risk, and this information might also be added to product labels. Sara Moradi Tuchayi: http://orcid.org/0000-0001-408X Zxiao Wang: http://orcid.org/0000-0003-2627-6630 Jiajun Yan: http://orcid.org/0000-0003-3286-3268 Xuefei Bai: http://orcid.org/0000-0001-5344-9221 Lilit Garibayan: http://orcid.org/0000-0002-9266-0887 Barbara A. Gilchrest: http://orcid.org/0000-0001-9906-1898 XB is the founder and chief executive officer of B.A.I. Biosciences, the company marketing sunscreen products, and performed or supervised some of the experiments mentioned earlier. JY is a scientific advisor for B.A.I. Biosciences. BAG is a paid consultant for B.A.I. Biosciences. LG and SMT performed many of the experiments mentioned earlier at Wellman Laboratories, Massachusetts General Hospital with support from a grant to Mass General Brigham from B.A.I. Biosciences. This study was funded by B.A.I. Biosciences. Conceptualization: XB, BAG; Data Curation: SMT, LG, ZW, JY, XB, BAG; Formal Analysis: SMT, ZW, JY; Investigation: SMT, ZW, JY, XB; Methodology: JY, XB; Project Administration: LG, JY, XB: Resources: LG, JY, XB; Supervision: LG, JY, XB; Visualization: XB, BAG; Writing – Original Draft Preparation: BAG; Writing - Review and Editing: JMT, LG, ZW, JY, XB, BAG