Sunscreens: Misconceptions and Misinformation

Abstract

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 (Figure 1a). SPF as by the are with a amount of for in vitro and for in vivo 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). have that test when to sunscreen in their far less to than the amount for determination of the SPF rating in vivo 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 the amount of both UVB and UVA energy transmitted through the product to the skin (Figure and the SPF values for many such protection may not in but effects of protection across the UV and visible spectra are to ingredients are as or or such as and absorb UV characteristically in the UVB although some also have an absorption 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). of these to and their to absorb UV Because not absorb visible light, are on the skin and cosmetically sunscreen such as the or titanium dioxide, scatter wavelengths across the UV (290−400 nm) and visible (400−700 nm) may also absorb light of wavelengths depending on their which are in determined by their et al., Lin H. of and from 2006; PubMed Scopus Google Scholar). are and Unfortunately, the of protection on the amount as it for all and at amounts of the of visible light a white to the skin that is a by of light by is and absorption for PubMed Scopus Google Scholar). will be in the for to that the to light on the skin even at the more sunscreens their requiring the of the day to the of In it is well-documented that sunscreen ingredients can or and S. H. and to sunscreens. of a and of the PubMed Scopus Google Scholar) and are through skin et al., J. V. et of sunscreen application on of sunscreen a randomized clinical 2020; appears in PubMed Scopus Google Scholar) and can be in and et al., M. A. M. T. H. M. et are for of of J PubMed Scopus Google Scholar), and Lim, Lim H.W. of effects of and other sunscreen Am Acad Dermatol. Full Text Full Text PDF PubMed Scopus Google Scholar) and other adverse effects with regular long-term effects, such as damage to et al., E. and other or sunscreens based on the adverse effects of sunscreen ingredients on PubMed Scopus (31) Google Scholar; and Lim, Lim H.W. of effects of and other sunscreen Am Acad Dermatol. Full Text Full Text PDF PubMed Scopus Google Scholar), are also of and have led and the for to the or use of all sunscreens et al., N. S. J. UV to protect part of UV and their to and J Dermatol. 2020; PubMed Scopus Google Scholar). or titanium consumers are with a to use a sunscreen product potentially harmful to users and the or a sunscreen that typically a white and to on the users with a makeup-like a to this is the of a to a sunscreen that the white (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 to far less than Some sunscreen manufacturers to have the less of defined as the of a UV on the label as a to a product on the label as a This then the sunscreen product’s UVB and UVA II absorption requiring a of UV to the unwanted white In other such an is added as a to a sunscreen to its UVB and UVA II absorption the of its sunscreen for an of the products shown in and Sunscreens the of and to with or and the SPF SPF Sunscreen SPF SPF Sunscreen SPF Sunscreen SPF Sunscreen SPF SPF SPF Sunscreen SPF Broad Spectrum SPF Sunscreen SPF SPF SPF Food and Drug sun-protection are as if or more ingredients on the product label as a but are to a of UV light and/or to UV filters. In some sunscreen UV absorption profiles for such in a new Food and Drug sun-protection are as if or more ingredients on the product label as a but are to a of UV light and/or to UV filters. In some sunscreen UV absorption profiles for such The precise of all commercial sunscreens a address the possibility that a on the sunscreen label to the product’s UVB and UVA II we the following The sunscreen at the on the label of the marketed sunscreen as a was in laboratory in a standard sunscreen other UV and with the the the absorb UVB and UVA II (Figure is in the as UV and and is an of the UV (Figure in vitro skin of these ingredients (Figure using the standard as in that to human the absorption of sunscreen ingredients et al., J. V. et of sunscreen application on of sunscreen a randomized clinical 2020; appears in PubMed Scopus Google Scholar). results suggest that sunscreen users adverse effects of on their and/or on the may wish to labeled sunscreens as well as sunscreens with of filters. regulatory agencies might require that all or be in product labels or if shown to be as UV filters. have been the FDA-mandated sunscreen rating the often in vivo SPF (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 and arbitrary broad-spectrum that to consumers on the of UVA are by the that the current SPF rating suggests to consumers for among products of UVB of UVB of UVB or of UVB especially that the amounts of sunscreen not the labeled of protection in SPF for the UVB of the spectrum might better be as the of energy that as SPF than as the present SPF the lower value when the is than the currently (Figure UVA protection are far more to that the action spectra for the multiple delayed adverse effects are unknown and may well among different of the UV spectrum, New labeling or at least the present SPF and consumers to and of UVA and visible light protection as well as UVB protection in marketed labels provide a the of UV energy blocked by the sunscreen (Figure a area the range of other users or their could then or specific on the of specific for and long-term sun the action spectra for photoaging, and other as adverse effects of sun exposure, the rating could be modified to the new Finally, the of has been in sunscreen it be that the action spectrum for cutaneous is well-established and in the UVB range and The and Am Acad 2006; Full Text Full Text PDF PubMed Scopus Google Scholar). have shown that regular use of SPF sunscreens is not with likely requires UVB exposure and/or is from a or and is all this Invest Dermatol. 2010; 130: Full Text Full Text PDF PubMed Scopus Google Scholar). regular use of a broad-spectrum sunscreen would no and this might also be added to product A. is the and of the sunscreen and or some of the experiments is a for is a for and many of the experiments at with support from a to from This study was by and

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