It’s usually this time of year where we see a rash of stories in the press warning us of the dire perils of sunlight and the ‘essential’ nature of sunscreens in protection from it. This year was a bit different, though, in that I don’t think we’ve anything like the usual number of sun scare reports. Plus, this week, we saw in the UK considerable interest in a study that cast doubts about the ability of sunscreens to protect against malignant melanoma (generally, the most serious form of skin cancer).
The study was done in mice [1], and you can read a report about it on the BBC website here. The bottom line is that this study found that factor 50 sunscreen increased the time it took for light exposure to induce melanoma, but the melanoma developed all the same. The take-away message from the study has been ‘don’t rely on sunscreens, use other means to protect yourself from sunlight such as seeking shade and wearing appropriate clothing’.
We cannot always extrapolate the findings of animal studies to humans. However, taking the study at face value and assuming it does apply to us, should we be too surprised by the findings? Actually, no: while sunscreens can help us extend our time in the sun without burning, there is evidence that relying on them for the prevention of skin cancer may be misguided.
In 2000, the International Agency for Research on Cancer in France held a meeting to discuss the role of sunscreens in skin cancer prevention. A report of the meeting’s findings was subsequently published [1]. The Agency concluded that there was evidence that sunscreens could reduce the risk of squamous cell cancer (one of the three main types of skin cancer) but only if individuals did not use sunscreens to extend their time in the sun. Actually, a lot of people use sunscreens in just this way. When people coat themselves in sunscreen on the beach or by the pool, the usual intention is to allow them to stay longer in the sun without burning.
But what of the role of sunscreens in melanoma prevention? A press release generated from the meeting stated that:
Several relevant epidemiological studies have shown significantly higher risks for melanoma in users of sunscreens than in non-users. This paradoxical observation could in part be due to the fact that users of sunscreens deliberately spend more time in the sun than they would otherwise. Thus, the protective effect of sunscreens can be outweighed by overexposure based on the false assumption that sunscreens completely abolish the adverse the adverse effects of [ultraviolet] light. In light of these findings, [we] concluded that sunscreens prevent sunburns and may reduce the risk of squamous cell carcinoma, but only if they do not mislead people to extend their exposure to sunlight.
In another review of the role of sunscreens in skin cancer prevention it was concluded that:
…no melanoma study has shown convincingly that sunscreen use reduces the risk of melanoma [2].
The authors forward several theories for why this might be, including the fact that sunscreens may 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). The vitamin D-blocking effects of sunscreens is also cited, along with the potentially carcinogenic nature of certain chemicals used in sunscreens including avobenzone and ecamsule.
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”…“The fervor with which companies promote sunscreen can perhaps be traced to the profit that sunscreen sales bring.
Further cause for concern comes from a research linking sunscreen use with not just malignant melanoma, but basal cell carcinoma [the third main type of skin cancer] too [3].
Personally, I don’t advocate the widespread use of sunscreens, and have not used them myself for more than 20 years.
While I’m no fan of sunscreens, sunburn is still something that should be avoided if at all possible. My advice here is to employ physical (rather than chemical) protection. I am delighted that this most recent research [1] has meant more focus is being placed on this strategy.
Around water it’s especially important to protect the skin when the sun is baking hot. The use of specialised clothing for wearing in water is a very good idea, here, I think. Being in water is one situation where there is an argument for sunscreen on parts of the body that are at risk of burning that cannot be protected with clothing, such as the face and ears.
References:
1. Viros A, et al. Ultraviolet radiation accelerates BRAF-driven melanomagenesis by targeting TP53. Nature published on-line 11 June 2014
2. Vainio H, et al. Cancer-preventive effects of sunscreens are uncertain. Scandinavian Journal of Work and Environmental Health 2000;26(6):529-531
3. Berwick M. The good, the bad and the ugly of sunscreens. Clinical Pharmacology and Therapeutics 2011;89(1):31-33
4. Autier P. Sunscreen abuse for intentional sun exposure. Br J Dermatol 2009;161 Suppl 3:40-5
