Sunscreen applied at ≥ 2 mg cm ?2 ?2 during a sunny holiday prevents erythema, a biomarker of ultraviolet radiation‐induced DNA DNA damage and suppression of acquired immunity

摘要

Summary 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 ( CPD s) 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 CPD s ( 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 CPD s share action spectra, the data strongly suggest that optimal sunscreen use will also reduce CPD formation and UVR ‐induced immunosuppression.