Researchers assessed how much sun protection people actually receive, based on typical use. It is known that people do not receive the full benefit of sunscreen from ultraviolet radiation because they apply it thinner than the manufacturers recommend.
In the first experiment of its kind, the team assessed DNA damage in the skin after reducing sunscreen thickness to less than 2 mg/cm2 – the amount manufacturers use to meet their SPF score.
The results showed that sunscreen with a sun protection factor (SPF) of 50, applied in a typical way, would provide 40% of the expected protection at best. The findings have prompted the research team to suggest that consumers use a much higher SPF sunscreen than they see fit to ensure they are protected from sun damage.
As part of the study, scientists divided a cohort of 16 fair-skinned volunteers into two groups of eight — (three women and five men in each). One group received a single UVR exposure to simulate sunlight, in areas treated with high SPF sunscreen of varying thickness, ranging from 0.75 mg, to 1.3 mg to 2 mg/cm2.
The other group received admissions on five consecutive days – to mimic continuous vacation exposure. The amount of UVR exposure was varied over the course of the experiment to mimic the conditions in holiday destinations such as Tenerife, Florida and Brazil.
Biopsies of the UVR-exposed areas of skin showed that, for the group that was repeatedly exposed to UVR, significant DNA damage was found in the areas not receiving sun protection, even though the UVR dose was very low.
Damage was reduced when sunscreen was applied at a thickness of 0.75 mg/cm2 and significantly reduced when 2 mg/cm2 sunscreen was applied, even with much higher UVR doses.
Five days of high dose UVR exposure with the 2 mg/cm2 sunscreen showed significantly less damage than just one day of low UVR dose exposure without sunscreen in all samples.
