Let’s get one thing straight from the get-go. We are strongly in favor of safe and effective sunscreens. As kids we experienced too many sunburns. That’s because back then there weren’t any products with SPF (sun protection factor) numbers. What was available did not prevent sunburn and might have even made the situation worse. Does your modern sunscreen prevent skin cancer? The answer is more complicated than you might imagine.
How Good Are Sunscreens?
If the goal is to prevent sunburn, most modern sunscreens are great. Anything with an SPF of 15 or higher will generally do a splendid job of preventing a burn.
Sunburn isn’t the only problem with sun exposure, though. People who spend a lot of time in the sun will experience more wrinkling and skin damage. Dermatologists call this photoaging. It is not caused by too many photos!
Signs of photoaging include uneven pigmentation, hyperpigmentation (age spots) and actinic keratoses. That’s dermspeak for scaly skin patches brought on by too much sun exposure. Although great scientific evidence is lacking, there is reason to believe that sunscreens can be helpful against photoaging.
“In a randomized controlled trial in 46 adults of mean age 63 years old with a previous diagnosis of skin cancer and/or actinic keratoses, the percentage of solar elastosis were 30.1% after 24 months application of SPF29 UVB/UVA (short wavelength UVA2) sunscreen vs 39.4% in the placebo group.”
“Solar elastosis” means the skin loses its elasticity. It leads to wrinkling. We wish the study was bigger and lasted longer, but it suggests that sunscreens can “protect against wrinkles and uneven pigmentation.”
The experts note that:
“Compared to discretionary sunscreen users, daily SPF15+ sunscreen users had 24% less skin wrinkling and coarse skin. Daily use of a broad‐spectrum sunscreen (SPF30) in 32 subjects for 52 weeks significantly improved clinical signs of photoaging, e.g. crow’s feet, fine lines, mottled pigmentation, discrete pigmentation and evenness of skin tone.”
These were not exactly huge studies. The results were OK but not mind blowing. I was hoping for studies involving hundreds or even thousands of volunteers that went on for several years. I wanted to see extraordinary benefits…like 90% reduction in signs of aging, wrinkling and actinic keratoses.
Can Sunscreen Prevent Skin Cancer?
So, there is some evidence that sunscreen protects against photoaging. The really big question, though, is sunscreen vs. skin cancer! Most people also ask: does sunscreen prevent skin cancer?
The official word from the American Academy of Dermatology (AAD) is that:
“Sunscreen use can help prevent skin cancer by protecting you from the sun’s harmful ultraviolet rays.”
You cannot get any clearer than that. But does slathering on the sunscreen prevent skin cancer? Is there solid scientific proof to support the AAD position that you should use sunscreen every day you are outside and reapply it every two hours?
A Reader Had a Seemingly Simple Question: Will Sunscreen Prevent Skin Cancer?
We stirred up a hornet’s nest when we answered a reader’s question about sunscreen.
“It seems to me that sunscreens may prevent burning, but I’m not sure they prevent skin cancer. The incidence of all types of skin cancer has increased since sunscreens were introduced.”
Here is a link to the original question and answer that was stimulated by this reader.
This fundamental question is surprisingly controversial. We imagined that there would be dozens of large randomized controlled trials proving unequivocally that sunscreen use prevents all types of skin cancer. That would include both melanoma and non-melanoma cancers such as squamous and basal cell carcinoma. Of course, we assumed the data would be convincing.
To our surprise, though, the medical literature does not provide a clear answer to the question of cancer prevention. A systematic review published three years ago found no association between skin cancer risk and the use of sunscreen (European Journal of Dermatology, April 1, 2018). In 29 different types of studies, people using sunscreen were neither more nor less likely to develop skin tumors.
Pause for a moment please. This is not some fly-by-night publication. The European Journal of Dermatology is peer reviewed and internationally renowned.
We also searched the Cochrane Database of Systematic Reviews (July 25, 2016). This organization is one of the most independent and trusted sources of medical evidence. Read about Cochrane at this link.
Cochrane Asks: Does Sunscreen Prevent Skin Cancer?
In trying to answer the question does sunscreen prevent basal or squamous cell skin cancer, the authors reviewed the available literature and found only one study worthy of analysis:
“We included one RCT [randomized controlled trial] that randomised 1621 participants. This study compared the daily application of sunscreen compared with discretionary use of sunscreen, with or without beta-carotene administration, in the general population. The study was undertaken in Australia…”
“In this review, we assessed the effect of solar protection in preventing the occurrence of new cases of keratinocyte cancer. We only found one study that was suitable for inclusion. This was a study of sunscreens, so we were unable to assess any other forms of sun protection…
“We were unable to demonstrate from the available evidence whether sunscreen was effective for the prevention of basal cell carcinoma (BCC) or cutaneous squamous cell carcinoma (cSCC).”
The Old Australian Study:
The biggest randomized controlled trial was conducted in Australia, where dermatologists have promoted a “slip-slap-slop” message for decades. Slip on a (long-sleeved) shirt, slap on a (wide-brimmed) hat and slop on the (high SPF) sunscreen. Researchers there reported that daily sunscreen application for more than 4 years significantly reduced the number of squamous cell cancers (The Lancet, Aug. 28, 1999).
Check the date. That was over two decades ago. The ingredients in sunscreen have changed quite a bit.
After an additional eight years of follow-up, the scientists reported that squamous cell cancers were down by nearly 40 percent among the volunteers assigned to daily rather than discretionary sunscreen use (Cancer Epidemiology, Biomarkers & Prevention, Dec. 2006). However, although these folks appeared to have fewer basal cell carcinomas, the difference was not statistically significant. Ten years after the end of the trial, only half as many people who had used sunscreen daily had developed melanoma (Journal of Clinical Oncology, Jan. 20, 2011).
What About Sunscreen vs. Melanoma?
Basal cell and squamous cell carcinoma are serious cancers, but they are common and rarely life-threatening if discovered early and treated appropriately. Melanoma is a different matter. This skin cancer can be lethal. That is why it is so important to try to prevent melanoma.
Another meta-analysis examined whether sunscreen use reduces the risk of melanoma and non-melanoma skin cancer. The outcome was also inconclusive (European Journal of Dermatology, April 1, 2018).
The authors wrote:
“While the current evidence suggests no increased risk of skin cancer related to sunscreen use, this systematic review does not confirm the expected protective benefits of sunscreen against skin cancer in the general population.”
Dermatologists Are NOT Happy With Us!
Not surprisingly, some dermatologists were dismayed by this message. One wrote:
“After spending over 40 years treating skin cancer and counseling patients on sunscreen use, I feel that the ‘data’ you reported needs interpretation in real life terms.
“Sunscreen use in many studies does not necessarily mean adequate use. A good British study done years ago showed that the average person applies only about 25 percent of the recommended amount of sunscreen. I suspect that the subjects in the studies you cited did not apply sunscreen half an hour before going outside, reapply it every two hours, or put it on more often if they were swimming or perspiring.
“My favorite advice to patients is if you can see without a flashlight, you should have sunscreen on.”
Not Enough Sunscreen?
One reader shared the dermatologist’s skepticism about the sunscreen studies. She wrote:
“What if the positive correlation between sunscreen use and skin cancer were caused by overconfidence of sunscreen slappers-on so that they stayed in the sun much longer than the non-slappers-on? Did the studies include average time spent in the sun, and time of day outdoors?”
She might very well be right.
Another reader chimed in:
“As a result of reading your article, I checked the labels on all our sunscreen bottles. They claim to prevent sunburn but say nothing about skin cancer.”
Where Are the Modern RCTs That Answer: Does Sunscreen Prevent Skin Cancer?
One of the authors of the original Australian study admits that randomized controlled trials (RCTs) are essential to answer the question whether sunscreens prevent skin cancer (Journal of Cosmetic Science, July/Aug. 2020). That’s because “observational evidence is intractably confounded.” In other words, it is not trustworthy. The only meaningful RCT remains the Australian study that was conducted between 1992 and 1996.
We are not suggesting that people should avoid sunscreen. Quite the contrary. But if we believe in evidence-based medicine, we really do need large, well-controlled clinical trials using modern sunscreens for the 21st century. Why hasn’t the very lucrative sunscreen industry sponsored such studies?
Avoiding the immediate pain of a sunburn is in itself worthwhile. But if we want to prevent the much greater and longer-lasting harm of skin cancer, especially life-threatening melanoma, we’ll need better research to answer the question: Does sunscreen prevent cancer?
If the sunscreen industry won’t conduct clinical trials, then the American Academy of Dermatology should sponsor a very large, well-controlled RCT (with optimal sunscreen applications) to show us whether sunscreens are truly effective at preventing skin cancer!
We live in an era of “evidence-based medicine.” That means physicians are supposed to rely on solid science to inform their recommendations. The public deserves better research when it comes to answering the question: does sunscreen prevent skin cancer?
We also need better studies to prove that sunscreens are safe. FDA-sponsored research a few years ago revealed that ingredients in sunscreens are absorbed into the body. Just recently a study suggested that sunscreens containing the ingredient octocrylene may be contaminated with benzophenone, a potential carcinogen. You can read about it at this link.
While We Wait:
In the meantime, perhaps we should all follow some simple common-sense approaches. Don’t go out in the sun between 10 and 2, when you are more likely to suffer a sunburn.
Use a hat with a brim, a long-sleeved shirt and long pants for protection if you must venture out. (If that sounds too hot, as well as too old-fashioned, look for some of the specialty clothing that has ultraviolet protection built in.)
When you put on your hat, don’t forget your sunglasses. And be aware that some popular medications may increase the likelihood of a sunburn. The diuretic hydrochlorothiazide (HCTZ), for example, has been linked to an increased risk of squamous cell skin cancer (Journal of the American Academy of Dermatology, April, 2018).
Read more about HCTZ and skin cancer at this link:
Share your thoughts about sunscreen in the comment section below. We especially welcome data from dermatologists that might answer the question: does sunscreen prevent skin cancer? If you cannot post a comment (our website has been acting badly for months), please be patient. Our web master promises to fix it very soon.
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Joe Graedon is a pharmacologist. Teresa Graedon holds a doctorate in medical anthropology and is a nutrition expert. Their syndicated radio show can be heard on public radio. Here is a link to the podcast so you can subscribe for free.