An article in the British Journal of Dermatology claims that there is a lack of evidence demonstrating the ability of modern sun protection products to prevent melanoma.
The author, Professor Brian Diffey from the department of Dermatology at Newcastle University, says that recent meta-analyses of observational case control studies have demonstrated no association between sunscreen use and either the prevention of the development of malignant melanoma.
There are some scientists who even believe that sunscreen might actually cause melanoma. For example, Octocrylene can penetrate into the skin and act as a photosensitizer, resulting in an increased production of free radicals. Free radicals can induce indirect DNA damage and potentially contribute to the increased incidence of malignant melanoma in sunscreen-users compared to non-users. Although this might theoretically apply to other sunscreens, the study
that made this conclusion refers only to octocrylene.
Nonetheless, Prof Diffey says this lack of conclusive evidence to prove sunscreen efficacy should not stop it from being recommended as a preventative measure.