Crux of Sunbathing and circadian rhythms by Jamie Scott:

  • XPA is a protein that repairs damage to DNA from sun exposure.
  • In mice (an animal that is active at night) more XPA is produced in the evening, and so mice that are exposed to sun radiation in the evening has smaller risk of skin cancer than mice exposed in the morning.
  • Since humans are active during the day, we may produce more XPA in the morning and so be less likely to develop skin cancer from morning sun exposure.