A short strand of DNA could become the sunscreen of the future, according to US researchers.
Applying DNA to the skin could help prevent cancer.
Scientists at Boston University School of Medicine found a DNA fragment called pTT can help repair and prevent skin damage caused by UV radiation.
PTT triggers a protein, called p53, that suppresses the growth of tumours, and helps repair damaged DNA.
The findings were published in the Proceedings of the National Academy of Sciences.
Scientists exposed hairless mice to UV radiation through sunlamps.
Mice with pTT rubbed into their skin were six times less likely to develop a tumour.
The DNA fragment works by penetrating the skin, then mimicking a response normally caused by DNA damage, which triggers DNA repair enzymes.
This means when the skin is exposed to UV, the enzymes are already present in the cells to prevent damage, or help repair it.
Lead researcher Dr David Goukassian said they were "effectively telling the cells to cope better with the UV".
He said this could have strong implications for anyone with fair skin or the elderly, who were at high risk from UV related skin damage.
"I wouldn't be wrong if I said that most British people and Celts (in general, people of Northern ancestry) are at high risk," he told BBC News Online.
"We hope that this could lead to new treatments being developed and we are working on it as fast as we can."
Previous studies have highlighted the ability of pTT to help skin cells, but this is the first to show how it works in a live animal.
Dr Goukassian said the next step will be to trial the process on humans.
According to Cancer Research UK, around 69,000 people in the UK are diagnosed with skin cancer each year.
It is also the most common cancer, primarily caused by the sun's harmful UV rays.
Dr Emma Knight, Science Information Officer for Cancer Research UK, welcomed the study but said it would be a long time before any treatments could be developed from it.
"The results of this latest study are promising, but the research is at a very early stage and much more work is needed."