New Methodology to Evaluate Sunscreens Under Outdoor Conditions: A Double-Blind, Randomized Intra-Individual Clinical Study of a Water-Based Broad-Spectrum SPF50+ Versus SPF15 (P3) and SPF50

Integrated sun protection advice for the South African population

Exposure to solar ultraviolet radiation (UVR) is associated with several cutaneous adverse effects. However, to the best of our knowledge, in South Africa there are no formal guidelines on sun protection. A group of South African dermatologists and researchers convened over the course of 1 year to deliberate on integrated advice for sun protection among the multi-ethnic South African population. For people with light skin and those with genetic skin disorders (e.g., oculocutaneous albinism), sun protection was identified as critical to prevent sunburn, skin cancer, and photoaging. The evidence is less clear for people with medium and darker skin types, especially the latter, in whom melanin may confer a degree of protection against some parts of the solar spectrum. Recent studies have demonstrated that visible light can cause pigmentary changes in individuals with darker skin types in particular. Sun protection for people of all skin colors is beneficial to protect against photoaging and ocular damage. Herein sun protection advice is suggested for South Africans of all skin colors to reduce morbidity and mortality from sun exposure, particularly relating to skin cancer. Several knowledge gaps are identified as future research priorities.

Evaluation of a Sunscreen Product Compared with Reference Standards P3, P5 and P8 in Outdoor Conditions: a Randomized, Double-Blinded, Intra-individual Study in Healthy Subjects

INTRODUCTION

The shortcomings of standardized sunscreen testing have been discussed in recent years, noting differences between how sunscreens perform in indoor clinical (in vivo) laboratory testing compared with real-life conditions. We previously developed an outdoor clinical method for ranking sunscreens by performance level. We used this method to test the performance of a new broad-spectrum sunscreen against International Organization for Standardization (ISO) reference products P3, P5 and P8.

METHODS

Sixty-five healthy volunteers with individual typology angle (ITA) ≥ 28° (light to intermediate skin colour) participated in an outdoor study in Mauritius. Test areas were marked on their backs, which were treated with the different products: one commercially available broad-spectrum sun protection factor (SPF) 50 sunscreen [investigational product (IP)] and the three reference products P3 (SPF 15), P5 (SPF 30) and P8 (SPF 50+) from ISO norm 24444:2019 for SPF testing. The test areas were exposed for 2-3 h, depending on the baseline skin colour. They were also compared with an unprotected positive control area and a non-exposed negative control area. Clinical and colorimetry assessment of erythema and pigmentation were performed at 24 h and 8 days, respectively.

RESULTS

Overall, according to this outdoor clinical testing method, the sunscreens' efficacy was ranked in an appropriate order given their established SPF levels, with higher SPFs giving greater protection against erythema and pigmentation. Between the different levels of SPF, the differences were statistically significant, for both clinical and colorimetry assessments. The new broad-spectrum SPF 50 IP performed similarly to the SPF 50+ (P8) reference product. Even the highest SPF products, SPF 50 and SPF 50+, had some instances of photoprotection failure.

CONCLUSION

These findings confirm the feasibility of this outdoor clinical testing method in ranking sunscreens and provide further evidence, in addition to standardized SPF and UVA protection factor (UVAPF) testing, on how this new broad-spectrum SPF 50 sunscreen performs in extreme outdoor solar exposure: in line with reference product P8 (SPF 50+).

TRIAL REGISTRATION NO

ISRCTN95394014.

[Characterization of sun protection performance: Quo vadis?]

Die Aufgabe der ersten Sonnenschutzmittel war es, die Entstehung von Sonnenbrand zu verhindern und, dem Zeitgeist der 1950/60er-Jahre folgend, die Bräunung der Haut nicht zu beeinträchtigen. Schnell entstand die Notwendigkeit, die Schutzleistung zu quantifizieren. Ursprünglich unter Zuhilfenahme des natürlichen – heute eines künstlichen – Sonnenlichts wurde eine Methode zur Bestimmung eines Sonnenschutzfaktor (SPF) entwickelt. Dieser ist heute formal als das Verhältnis zwischen minimaler erythemwirksamer UV-Dosis auf mit Sonnenschutzmittel geschützter und minimaler erythemwirksamer UV-Dosis auf ungeschützter Haut definiert (ISO 24444:2019). Drei Beobachtungen stellen die Eignung der Methode infrage: 1) Zwischen-Labor-Variabilität: Trotz strenger Normierung sind Resultate von SPF-Bestimmungen aus verschiedenen Labors und Regionen sehr großen Schwankungen unterworfen. 2) Natürliches vs. künstliches Sonnenlicht: Das Strahlungsspektrum des künstlichen Sonnenlichts unterscheidet sich von dem des natürlichen Sonnenlichts. Die mit künstlichem Sonnenlicht bestimmten SPFs (wie auf allen derzeit im Handel befindlichen Sonnenschutzmitteln abgebildet) sind im Vergleich zur SPF-Bestimmung mit natürlichem Sonnenlicht deutlich zu hoch. 3) Erythembelastung: Bei der Bestimmung des SPF werden die Probanden potenziell schädlicher Strahlung ausgesetzt. Vor diesem Hintergrund werden alternative Methoden – In-vitro-SPF, hybride diffuse Reflexionsspektroskopie (HDRS) und In-silico-Berechnungen – vorgestellt. Diese haben das Potenzial, die heutige mit erheblichen Einschränkungen verbundene Methode abzulösen. Als Sofortmaßnahme wird die Rückbesinnung auf die für alle verständliche Beschreibung niedriger, mittlerer, hoher und sehr hoher Schutz empfohlen, in Zukunft unter Berücksichtigung des Spektrums des natürlichen Sonnenlichtes.

Outdoor sunscreen testing with high-intensity solar exposure in a Chinese and Caucasian population

BACKGROUND

Currently, sunscreens' sun protection factor (SPF) and ultraviolet (UV) A protection are tested separately under indoor conditions, without considering external conditions that may affect performance. Studies are often conducted in Caucasian individuals; other racial groups may respond differently.

METHODS

An outdoor, double-blind, intra-individual study was performed in 63 healthy Chinese and Caucasian volunteers in Singapore. Subjects underwent one outdoor sun exposure lasting 2-3 hours. ISO reference products P3 (SPF 15), P5 (SPF 30), and P8 (SPF 50+) applied at 2 mg/cm² were compared against each other and against an untreated exposed area (positive control) and an unexposed area (negative control). Endpoints were investigator global assessment (IGA) of erythema at 24 hours, IGA of pigmentation at 1 week, and colorimetry (a*, L*, and ITA) at 24 hours and 1 week.

RESULTS

Clinical erythema and pigmentation scores were statistically significantly different among the three sunscreens, with the highest SPF product providing the highest protection, confirming the discriminatory capacity of the model used. Colorimetric assessment correlated well with clinical evaluation.

CONCLUSION

This study confirmed the feasibility of ranking sunscreens (at 2 mg/cm² ) based on clinical effects of high-intensity outdoor solar radiation. Larger studies are needed to look at differences in erythema and pigmentation reactions between Chinese and Caucasian individuals, which could be relevant for photoprotection.

Photoprotection of the future: challenges and opportunities

The use of sunscreens is an important and essential component of photoprotection. Since their introduction during the first half of the last century, sunscreens have benefited enormously from major technological advances such as the development of novel UV filters; as a result, their efficacy in preventing UV-induced erythema is unequivocal. More recently, however, new challenges have appeared, which have prompted a robust discussion about the safety of sunscreens. These include topics directly related to photoprotection of human skin such as improved/alternative methods for standardization of assessment of the efficacy of sunscreens, but also many others such as photoprotection beyond UV, concerns about human toxicity and ecological safety, the potential of oral photoprotective measures, consequences of innovative galenic formulations. On a first glance, some of these might raise questions and doubts among dermatologists, physicians and the general public about the use sunscreens as a means of photoprotection. This situation has prompted us to critically review such challenges, but also opportunities, based on existing scientific evidence. We conclude by providing our vision about how such challenges can be met best in the future in an attempt to create the ideal sunscreen, which should provide adequate and balanced protection and be easy and safe to use.