An Australian study appears to have answered the burning question at the core of sun safety - can sunscreen actually help to prevent melanoma?
Despite evidence that sunscreen can protect against less lethal forms of skin cancer, its effect on the incidence of rarer but often deadly melanoma has remained unclear.
Complicating the research is the fact very fair-skinned people, who have the most cases of melanoma, were also most likely to heed the warning and so routinely slop on their sunscreen.
"People who are at naturally higher risk of melanoma are also naturally the people who use sunscreen," said Queensland Institute of Medical Research (QIMR) Professor of Epidemiology Adele Green.
"You can imagine then, this is very hard to disentangle whether there is a protective effect of sunscreen on melanoma.
"There can even be this confusing effect where ... there's more melanoma among people who use sunscreen."
So while sunscreen has long been recommended as a "precaution" against all skin cancers, the science on its effect on melanoma alone has remained "highly controversial".
That was until Prof Green's unique study, which tracked a group of just over 1600 residents in Nambour, Queensland, and it showed how wearing sunscreen every day cut their incidence of melanoma in half.
The adults were randomly allocated to either a control group - who continued as per normal and wore as much or as little sunscreen as they liked - or a group given an unlimited supply of sunscreen.
Those provided with free sunscreen were asked to apply it every morning to their head, neck, arms and hands and the trial ran for five years to 1996.
Monitoring over the next 10 years found identified 22 cases of melanoma in the control group, and 11 cases among those who wore sunscreen every day.
Prof Green said while the result appeared to be conclusive it was too early to declare the sunscreen-melanoma debate as over.
"I wouldn't say that on the strength of one study but this has to be reassuring at this stage," she told AAP.
"... to medical professionals, public health authorities and the general public, that the regular application of sunscreen is likely to be beneficial with regard to melanoma protection."
There are three major types of skin cancer, with melanoma the least common but most often lethal as the cancer could spread from its initial site on the skin to generate tumours elsewhere in the body.
The other types - basal cell carcinoma or squamous cell carcinoma - were more regularly seen but were less likely to spread and so were not usually life-threatening if detected early.
There are more than 10,000 cases of melanoma diagnosed every year in Australia, which shares the world's highest incidence of melanoma along with New Zealand.
More than 430,000 Australians are treated every year for non-melanoma skin cancer.
The paper is published on Tuesday in the Journal of Clinical Oncology.
