Background Most epidemiological data of sunburn related to skin cancer have come from self-reporting in diaries and questionnaires. We thought it important to validate the reliability of such data.
Objective To validate the quality of self-reported erythema by sun worshippers and skiers, and to validate the ability to determine erythema visually compared with objectively measured erythema.
Methods The skin in a group of sun worshippers in Tenerife and of skiers in Austria was closely monitored over a week. The participants used a diary to record any erythema assessed on different skin sites and underwent a twice daily skin examination by researchers who assessed erythema on the same sites. Lastly, the erythema assessment was validated by objective measurements.
Results We found that the participants’ agreed with researchers’ assessment of erythema in only 57–61% of cases, and that the researchers detected up to 28% more of the objectively measured erythema than the participants did. We also found that, even for the trained eye (researchers), it was difficult to detect an increase in erythema as only 71–91% of those cases with an increase >15 in measured erythema percentage were detected in the evening. Possibly, detection was impeded by a simultaneous increase in pigmentation.
Conclusion Self-assessment of erythema from diaries is unreliable. Erythema is considerably underestimated and possibly neglected. Even for the trained eye, it can be difficult to detect erythema.