over-exposure

http://www.yourrunning.com/blog-skin_cancer_stop_beating_up_your_immune_...

News that marathon runners and other endurance athletes may be at increased risk of skin cancer shouldn’t have come as a surprise.

Mainstream media focused on the idea that it was increased exposure to the sun that was to blame, and almost universally carried warnings for runners to slap on the sunblock. In doing so they completely missed the point – which is that training and racing suppresses the immune system.