1171 Identifying factors affecting UV sensitivity by minimal erythema dose testing in over 20,000 individuals

Abstract

UV sensitivity plays an important role in diagnosis and treatment of skin diseases. It is normally measured by the minimal erythema dose (MED) testing. There is known individual variations in MED. However, despite of wide interests and many previous attempts, there is no consensus on the factors affecting the individual variations in MED – probably because of the limitation of sample size. Here we carried out a large scale study testing MED in 20,898 individuals aged 20-60 in China (mostly Fitzpatrick skin type II and III). MED was measured on lower back by following standard protocol. We found that men have higher MED than women (p<0.01). Darker skin is normally associated with higher MED, explaining much of the gender difference (p<0.001). MED increases with age (p<0.01). Furthermore, MED is the highest in winter and lowest in summer, with temperature being the main influencing factor (r=-0.27, p<0.001). In conclusion, our data suggests that UV sensitivity – measured by MED – can be affected by age, gender, skin color and season. These factors should all be considered in the study design of UV sensitivity tests.