The study by Cancer Research UK found that while high-factor sun cream can reduce DNA damage caused by the sun and slow the onset of malignant melanoma, it does not offer full protection. It proves campaigns are right to promote a combination of methods such as hats and shade alongside sun cream, scientists said.
During the study, mice who were predisposed to melanoma took only around 30% longer to develop cancer when coated in SPF 50 sun cream than those who were not. The research, published in the scientific journal Nature, revealed that UV light directly damages DNA in the skin's pigment cells, which increases the chance of developing the disease.
Scientists discovered that UV light also causes faults in the gene which normally helps to protect against sun damage.
Professor Richard Marais, study author and Cancer Research UK scientist, based at the University of Manchester, said: "This work highlights the importance of combining sunscreen with other strategies to protect our skin, including wearing hats and loose-fitting clothing, and seeking shade when the sun is at its strongest."
Dr Julie Sharp, head of health information at Cancer Research UK, warned that people exposed to sunlight must wear a cream with good UVA protection.
She said: "This research adds important evidence showing that sunscreen has a role, but that you shouldn't just rely on this to protect your skin."