UK scientists say they have developed a sunscreen that will actively repair sunburnt skin and may even help prevent skin cancer.
The lotion is undergoing lab testing
Like conventional suncreams, the lotion filters the sun's harmful rays.
But an extra ingredient means it also helps mop up the free iron released when skin burns, the Bath University team found.
This reduces inflammation, pain and prevents the build up of cancer-causing free radicals triggered by sunlight.
The new ingredient - called a chelator - is light-responsive, meaning it only becomes active when it is exposed to UV radiation in sunlight.
This should avoid any side effects that might result from long-term exposure to the active form of the drug, the authors told the Journal of Investigative Dermatology.
Dr Charareh Pourzand, along with colleagues at Nottingham University, is currently testing prototypes of the ingredient in the laboratory, but expects to begin human trials in the next two to three years.
She said: "When skin is exposed to high doses of sunlight, such as when you are sunbathing, a massive amount of free iron is released in skin cells.
"This free iron can act as catalysts for the generation of more harmful free radicals that cause severe cell damage.
"Many forms of cancer are thought to be the result of reactions between free radicals and DNA, causing mutations that can disrupt the cell cycle and potentially lead to cancer.
"We wanted to find a way of mopping up sunlight-generated free iron that produce harmful radicals during exposure to bright sunlight in order to prevent the unwanted side reactions that can lead to skin damage and ultimately cancer."
She said the best way to do this was to use chelators - drugs that bind and export iron from the body.
"However, long term use of chelators can be toxic for cells as it starves them of the iron necessary for normal biological processes, for example the red blood cells that transport oxygen around the body need iron to work," he said.
The researchers hope that new sunscreens containing these components will also last longer than conventional sunscreen lotions.
Dr Emma Knight of Cancer Research UK said: "This is an interesting study but the research is still at a very early stage.
"Much more work is crucial before we will know whether this approach has potential for preventing skin cancer.
"When we are trying to protect ourselves from sunburn and skin cancer, sunscreens should be used as a last line of defence.
"The most important thing is to avoid burning by spending time in the shade between 11-3, and covering up with a T-shirt, hat and sunglasses."