Sunscreens can get a bad rap from promoters of alternative medicine, often returning to the well used warnings about the dreaded Toxins. While being aware of what you apply to your skin is a good idea the scaremongering employed by these groups is almost certainly counter productive in terms of reducing cancer risk in those exposed to the harmful effects of the sun. To assert that the application of sunscreen itself actually causes cancer is to both willfully misinterpret the medical literature and engender ill founded paranoia in those that are susceptible to such tactics.
This is not to say that sunscreens are universally good or are a magic bullet for cancer prevention. There have been studies that found a positive correlation of cancer with screen use, however this is likely due to an over-optimistic attitude towards the capabilities of the screens as well as the fact that almost by definition people who use sunscreens tend to spend more time in the sun. Even so, my own opinion that the nuclear furnace that dominates our sky is over rated, is one that even today should probably not be encouraged.
With regards to use of sunscreens as well as outdoor activities in general it should be realised that a responsible attitude towards sun exposure is prudent, cover up and limit sun exposure when able and reapply sunscreen often. It is generally recognized that the light from our closest star is beneficial to our health in many ways but as with anything else moderation is the key and an overdose can have fatal consequences.
Resources
http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1447210
http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1070981
http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1180647
http://www.worldimage.com/blog/archives/000027_sunscreen_dangers.html some sunscreen bashing, luckily they sell their own.
http://www.lyricscrawler.com/song/3953.html -The “Sunscreen song” just because.
Scepticon 
Sorry for commenting on this old article but since Peter Dingle has raised the spectre of the sunscreen ogre on Australian national TV again this month, I wondered if you’d be willing to revisit the issue and write an update.
I’ve been battling the urge to write my views on the issue for weeks now and one thing that’s holding me back is a general lack of skeptical analysis of the “debate”.
To me, it looks very much like the mercury/vaccine argument but I’m in no position to offer advice, only opinion.
I just read this interview with Dr. Dingle, he made several claims about sunscreens, some looked like simple anti-sunscreen propaganda but there was a study done a few months back that did look at the effect of suncreen formulations on skin after absorbing UV rays that did find increased harmful effects. I’ll have to dig it up to see what the actual conclusions were.
The comments about toxins being absorbed through the skin and moving around in the blood to the breast tissue and testies etc. probably has a grain of truth but I would be surprised if the risks were greater than not wearing sunscreen in the Australasian climate.
I was aware of some sunscreen controversy a couple of weeks back but I had not heard of this guy’s involvement. I must say a look at his website doesn’t really fill me with confidence that he’s a reliable source. It seems to be straigh out of the scam artists handbook – what ever your problem, he’s got the answer.
Thanks for the tip I think I will look into this.