Background: Sun protection factor (SPF) is assessed with sunscreen applied at 2 mg cm −2 . People typically apply around 0·8 mg cm −2 and use sunscreen daily for holidays. Such use results in erythema, which is a risk factor for skin cancer. Objectives: To determine (i) whether typical sunscreen use resulted in erythema, epidermal DNA damage and photoimmunosuppression during a sunny holiday, (ii) whether optimal sunscreen use inhibited erythema and (iii) whether erythema is a biomarker for photoimmunosuppression in a laboratory study. Methods: Holidaymakers (n = 22) spent a week in Tenerife (very high ultraviolet index) using their own sunscreens without instruction (typical sunscreen use). Others (n = 40) were given SPF 15 sunscreens with instructions on how to achieve the labelled SPF (sunscreen intervention). Personal ultraviolet radiation (UVR) exposure was monitored electronically as the standard erythemal dose (SED) and erythema was quantified. Epidermal cyclobutane pyrimidine dimers (CPDs) were determined by immunostaining, and immunosuppression was assessed by contact hypersensitivity (CHS) response. Results: There was no difference between personal UVR exposure in the typical sunscreen use and sunscreen intervention groups (P = 0·08). The former had daily erythema on five UVR-exposed body sites, increased CPDs (P < 0·001) and complete CHS suppression (20 of 22). In comparison, erythema was virtually absent (P < 0·001) when sunscreens were used at ≥ 2 mg cm −2 . A laboratory study showed that 3 SED from three very different spectra suppressed CHS by around ~50%. Conclusions: Optimal sunscreen use prevents erythema during a sunny holiday. Erythema predicts suppression of CHS (implying a shared action spectrum). Given that erythema and CPDs share action spectra, the data strongly suggest that optimal sunscreen use will also reduce CPD formation and UVR-induced immunosuppression.
Bibliographical noteFunding Information:
The European Commission (EC), under the Framework 7 Programme Environment Theme, funded the research, contract no. 227020: the Impact of Climate and Environmental Factors on Personal Ultraviolet Radiation Exposure and Human Health (ICEPURE). The EC and Walgreens Boots Alliance Inc. paid for the full cost of the holidays. Specifically, Walgreens Boots Alliance Inc. supported the sunscreen intervention studies. The research was also funded by the Medical University of Łodz, Poland, research project number 503/5-064-01/503-01 and the U.K. National Institute for Health Research (NIHR) Biomedical Research Centre based at Guy’s and St Thomas’ NHS Foundation Trust and King’s College London, U.K. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the U.K. Department of Health and Social Care. Walgreens Boots Alliance Inc. supplied the sunscreens for the intervention studies and selected their sun protection factor for the expected weather conditions in Tenerife during the study.
© 2018 The Authors. British Journal of Dermatology published by John Wiley & Sons Ltd on behalf of British Association of Dermatologists.