Spending only short lengths of time in the sun suppresses the immune system in humans, according to European researchers. Although the effects of solar radiation have been known for some time, this is the first time the effects of low level, 'everyday' exposure have been studied. 

Groups of volunteers were exposed daily to low doses of radiation - similar to sunlight - for up to 30 days.  

Joanna Narbutt from the Medical University of Lodz, Poland, and colleagues then tested the volunteers' responses to the allergen, diphenylcyclopropenone. Those irradiated for the full 30 days showed the smallest allergic response, which meant their immune systems were suppressed. 

The radiation doses were equivalent to just 15 minutes in the summer sun. The immune systems of the people exposed to the maximum radiation dose showed no signs of adapting to the conditions. 'This indicates the necessity of using sunscreens during everyday exposure' said Narbutt.  

Vikki Allen