Epidermal DNA repair under repeated exposure conditions is complex

We thank Hemminki and Snellman (2002) for their interest in our studies and we are pleased to be able to clarify the issues they raise. The main purpose of our study (Sheehan et al 2002), as indicated by the title of the paper, was to determine the photoprotective properties of induced pigmentation by solar simulated radiation (SSR) in skin types II and IV. We used individual biological [just perceptible minimal erythemal doses (MED)] dose increments rather than fixed physical (J/cm2) doses because individual exposure in real-life is determined by sun-sensitivity. This is supported by recent studies, in which personal exposure has been electronically monitored over 114 days, that show that skin types IV have about 40% more solar UVR-exposure than skin types II (Thieden E. & Wulf H.C., personal communication).