Slap on more sunscreen or increase SPF, say scientists

Sunscreen that is spread on the skin too thinly may provide less than half the expected degree of protection, a study has shown.

Scientists analysed DNA damage from ultraviolet (UV) rays in the skin of volunteers at various levels of sunscreen thickness.

They found that sunscreen lost much of its effectiveness if applied below the recommended thickness of two milligrammes per square centimetre of skin (2mg/cm2).

That is the thickness level on which manufacturers’ sun protection factor (SPF) ratings are based.

But people are known to be far more conservative in their use of the creams and lotions. Previous studies suggest that sunscreen is typically spread as thinly as 0.8mg/cm2.

The new study, led by King’s College London, showed that at this level of usage, a sunscreen with a high SPF of 50 would at best provide 40 per cent of expected protection.