Sun worshippers may be increasing their risk of developing skin cancer by using sunscreens that encourage them to stay too long in the glare, researchers say.
Sunburn has long been regarded as an important cause of melanoma, the most serious form of skin cancer, especially in children under 15. But some experts argue that the real risk comes from spending too long in the sun, and that using sun creams to protect against sunburn may instead promote the cancer.
More than 5,000 cases of melanoma are reported each year in the UK and more than 1,600 deaths. The incidence of the disease has trebled in recent decades, which is thought to be linked with the growing popularity of foreign holidays.
Sunscreens have been heavily promoted as a means of protecting sunbathers but they may have the opposite effect, according to a report in the Journal of the National Cancer Institute. It cites Antony Young of King's College, London, who said several large scale studies over the past few years had been "unable to tease out any clear relationship" between sunscreen use and melanoma incidence. But some studies showed sunscreens increased the incidence of melanoma.
Research by Philippe Autier of the European Institute of Oncology in Milan suggests melanoma may be at least a two- stage process, with different kinds of solar radiation causing new moles in childhood and their growth into larger moles that later become cancerous.
Over the past decade, he has become convinced that sunburn is "probably not part of the mechanism of cancer". It may simply be a marker of people with sensitive skins who are more prone to skin cancer and who have spent too long in the sun. Sunburn may even protect against melanoma - by keeping people out of the sun.
Lying in the sun longer, especially at midday when the ultraviolet rays are strongest, may raise a person's exposure above what it would have been without sunscreen. It is this intense, intentional time in the sun that is most closely linked with melanoma risk, Dr Autier said.
The only way to reduce the risk of melanoma may be to hide from the sun in the shade, cover up with a hat and long-sleeved shirt, or stay indoors.