Too much sunlight can cause sunburn, and sunburn is a risk factor for skin cancer. So, if sunscreens help prevent sunburn, they should reduce the risk of skin cancer too, right? It turns out, according to a piece appearing last month in the journal Clinical Pharmacology and Therapeutics, that the evidence that sunscreens protect against skin cancer turns out to be a bit thin on the ground [1].
Skin cancers come in three main forms: the quite-often deadly malignant melanoma, as well as squamus cell carcinoma and basal cell carcinoma that are not nearly as life-threatening. 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. The study looked only at squamous cell and basal cell carcinomas. 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.
Turning out attention for a moment to malignant melanoma, the article states: “Unfortunately, no melanoma study has shown convincingly that sunscreen use reduces the risk of melanoma.” The piece goes on to speculate why this might be. A few theories are put forward, which include:
- The sorts of people who use sunscreen (e.g. fair-skinned) are generally at enhanced risk of skin cancer to begin with.
- Sunscreens often protect against burning by blocking ultraviolet B (UVB) rays, but may allow longer exposure to potentially damaging rays from other parts of the spectrum such as UVA.
- Many people who use sunscreens do not apply them properly.
- Sunscreen may block the manufacture of vitamin D (which is linked to cancer-protective effects). This mechanism is viewed as of doubtful significance by the author, who refers to the fact this is only likely to an issue in those who apply the sunscreen properly.
- The potentially carcinogenic effect of certain chemicals used in sunscreens including avobenzone (Parsol 1789) and ecamsule (Mexoryl SX).
The article goes on to refer to the fact that “…interests that are not scientifically based seem to be driving the heavy reliance on sunscreens as the first line of prevention against skin cancer,” adding “The fervor with which companies promote sunscreen can perhaps be traced to the profit that sunscreen sales bring.”
The piece also states: “Death from skin cancer is advertised as being avoidable with the use of sunscreens. This position might actually be true, but there is as yet absolutely no scientific evidence to support it.”
For more information on safe sun exposure including the use of clothing and shade, see here.
References:
1. Berwick M. The good, the bad and the ugly of sunscreens. Clinical Pharmacology and Therapeutics 2011;89(1):31-33
As melanoma is related to burning, try to not get burned. Basal & squamous cell carcinomas are related to cumulative UVB (& UVA) exposure. However, the risk factor for more serious cancers falls with increasing cumulative UVB exposure. See
A meta-analysis of second cancers after a diagnosis of nonmelanoma skin cancer: additional evidence that solar ultraviolet-B irradiance reduces the risk of internal cancers.
Does solar exposure, as indicated by the non-melanoma skin cancers, protect from solid cancers: vitamin D as a possible explanation.
Dr Briffa, revisiting the [ .. link ..] to the earlier blog I was reminded how interesting the subject is and how that particular thread developed in discussion.
I’m not at all surprised.
Although I would like to see how much the intervention effected cancers other than skin cancer, and the participants’ general health.
If sunscreen reduces the amount of Vit D produced in the skin, you could speculate that sunscreen would increase risk of other cancers that Vit D has been shown to help protect against.
Australians have some of the highest skin cancer rates in the world and they have been lathering on sunscreen for decades. Is it possible that the sunscreen is actually aggravating the tendancy towards skin cancer?
I believe sunscreens have a function, especially at the beginning of the season, while getting used to the suna again, and in windy conditions, to stop the skin from drying out. Overall, however, I think it is better to manage exposure to the sun, rather than relying on sunscreen. On our sun terrace, we have a canopy of bamboo canes, which cuts out about 80 percent of the direct sunlight but allows through enough to develop a nice tan, without ever burning.
I wish this article could be published in every newspaper and journal. We need a ‘bus stop’ moment for all the people who say that using high factor sun screen like emulsion paint is the safest way. I get tired of being told to keep my advice to myself as I’m not a doctor. All I do is suggest that they read up the subject. They have to be converted because they want to be.
We could not go on a coach tour in Queensland unless we were clutching our 50 factor sun screen. In todays paper they are not mentioning Vit D3 as a protection to breast cancer, but lots of other strange reasons. Don’t the medical profession ever read anyone elses research?
What is known about the safety and efficacy of the nano-particle sunscreens now in vogue and being used heavily in Australia? If they penetrate the skin to provide invisible protection, where do they end up in the body? Does somebody out there know more about this?
Reminds me of an interesting graph I found: The incidence of skin cancers in Connecticut rose alarmingly in tandem with the sales of ever increasing factor sunscreens. In the fifties there was a flat line of skin cancers, but as the sun screens came on the market, the cancers proliferated.
Why is it not possible for all interested groups looking for natural health remedies & preventions to get together to make a greater impression on the drug manufacturers and government heath organisations to listen to the practical evidence.
http://www.naturalnews.com/SpecialReports/Sunlight.pdf
Or is a conflict of commercial intrests
It’s also worth pointing out that the consumption of polyunsaturated fats is enormously high is Australia and there are doctors who are pretty sure that there’s a link between it’s consumption and skin cancers.
Hooray for the mention of the dangers of Avobenzone also known as butyl methoxydibenzoylemethane! I have a strong reaction to this particular ingredient — my eyes water, my nose runs, I start wheezing and my chest tights. It’s used extensively in most if not all cosmetics sporting an spf factor as well as in most sunscreens. Maybe now the cosmetics industry will sit up and do something about it but probably not!
As Robin Davies mentions the possible link between consumption of polyunsaturated fats and skin cancers, yes and all the other ‘chemical’ coctails we put into/onto our bodies. Is there not a layer of fat under our skin?? So when you ‘cook’ it and cause an inflammation response all the toxins stored in this fat have the potential to wreak havoc, and confuse our cells even more! I am of the understanding it is the UVB that we NEED to start the Vitamin D conversion.
This article appeared in a newspaper last year. Its author Sam Shuster is emeritus professor of dermatology at Newcastle University. It makes interesting reading but once again we are faced with the modern nightmare of not knowing who to believe.
http://www.dailymail.co.uk/health/article-1301722/The-melanoma-epidemic-Dont-panic–terrible-mistake.html
I have skin that burns easily but it totally irritated by sunscreen SPF ingredients so I manage my exposure to the sun. I actually found I burnt more with sunscreen on than off and that it irritates my skin to give the appearance of a rash of somesort. So I never use moisturiser with sunscreen in it and honestly don’t miss it. I think the sunphobics are actually as dangerous as the fatphobes and the sooner people start using their brains and researching the information out there the better. Listening to so called experts is the sure road to ill health and mis-information on a global scale, especially when it involves billions of dollars in profits to certain companies.
How come most of the melanomas one hears of, are under people-s nails, in their hair, or behind their knees, places not usually exposed to sun. If I put on sunscreen I itch, so I haven-t bothered, but I don-t sit out and bake either.Forgive my keyboard acting up.
Hi,
Thanks for this great article. I’m in a discussion with a doctor friend of mine who really fails to see the merit in the argument that sunscreen may contribute to skin cancer. I wanted to take a closer look at the reference you gave. I found the abstract of Pubmed but couldn’t dig any deeper. I’m new to trying to look at things there – do I have to sign up or something to be able to see the details of the research ?
Thanks for any help
Steven
Steven Lord,
Many medical and science journals require payment or a subscription for access to their articles. If you have a medical school nearby, you may be able to request a copy of the article through its library access. You might even have some luck through your local public library. Your doctor friend may have access to the journal’s articles, too.
http://drdingle.com/docs/sunsreens_final1.pdf
some discussion within the lecture regarding skin penetration and cream types
http://www.unisa.edu.au/knowledgeworks/Lectures/2009/michaelroberts.asp
does skin cancer arise from sun damage sustained ‘years ago’ as in more than the 4.5 years of the study?
here is that link : http://www.nature.com/clpt/journal/v89/n1/full/clpt2010227a.html it is free