The author of the Clinical Pharmacology and Therapeutics piece cites a randomised study in which individuals used daily sunscreen or no daily sunscreen for 4.5 years.
http://www.drbriffa.com/2011/02/03/arti ... in-cancer/The result was that the development of new cancers was essentially the same in both groups. In other words, the application of sunscreen did not appear to protect against the development of new skin cancers.
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