Does sunscreen actually prevent skin cancer?

It does successfully prevent sunburn, but what about the evidence for sunscreen protecting you from skin cancer later in life?

The answer: Nobody is really sure. Last year, I wrote a short piece for BoingBoing that looked at this a little bit. The key point: Cancer takes a long time to happen and we haven't been using sunscreen long enough to have much evidence about it.

But, at Discover's The Crux blog, Emily Elert expands on some of the other problems in play. One of the key things—and something that will hopefully be fixed by this time next year—there's nothing on the sunblock you buy to tell you how protective it is against skin cancer. SPF is all about the burn. So even if some sunscreens do protect against cancer, you don't have a good way to know whether or not you're using one of them.

First of all, the way sunscreen’s effectiveness is measured—its SPF rating—basically only describes its ability to block UVB rays. That’s because UVB is the main cause of sunburn, and a sunscreen’s SPF stands for how long you can stay in the sun without getting a sunburn (a lotion that allows you to spend 40 minutes in the sun rather than the usual 20 before burning, for example, has an SPF of 2).

UVA rays can cause cancer but not sunburn, so they don’t factor into the SPF calculation. That means that if you slather on a high SPF sunscreen that only protects against UVB, you’d still absorb lots of UVA radiation, potentially increasing your long-term cancer risk.

Soon it will be easier to tell which sunscreens include ingredients that block or absorb UVA as well as UVB. According to FDA regulations passed last year, products that pass a “Critical Wavelength” test—meaning that they block wavelengths across the ultraviolet spectrum—will carry the label “Broad Spectrum” alongside the SPF, while sunscreens that don’t pass the test will be forbidden from claiming they have such capabilities. However, those regulations don’t go into effect until December, so for this summer, you’re still stuck with SPF. And, by the way, you probably need to apply twice as much sunscreen as you think to actually get an SPF as strong as that marked on the bottle: manufacturers test their products’ SPF with the assumption that you will slather on obscene amounts. This discrepancy could be contributing to the fact that the NIH, when looking the connection between sunscreen use and skin cancer in large populations, doesn’t see clear evidence that sunscreen is effective in reducing the risk of skin cancer. (It’s worth pointing out, too, that there is a clear genetic component in some skin cancers, so just avoiding sun or using sunscreen regularly are not the only factors that determine whether someone gets it.)

Read the rest of the story at The Crux

Image: Beer, cigarettes and sun block: Roskilde Festival 2009 essentials., a Creative Commons Attribution (2.0) image from wouterkiel's photostream


  1. After reading about the incoming labeling regulations I started looking at the labels of the various sunscreens I have lying about (4-5 different brands, yea I tend to forget to bring them places and then buy another).  Every one of them, some a few years old, are uv-A and uv-B protecting.

    I’m thinking that the bad sort of sunscreen is actually pretty uncommon these days, or restricted to ultra cheap dollar store brands or something.

    1. Far from it!  And in fact, many of the cheaper sunscreens are the best.  The Environmental Working Group rates all the sunscreen brands every year, and it’s alarming how many high-end and common brands are terrible.

      One thing they also mention is that many sunscreens contain chemicals that actually have shown to INCREASE cancer risk when they are exposed to sunlight.  ie: Retinol, a very common sunscreen ingredient. We may actually be CAUSING skin cancer when using just “any old brand” of sunscreen, thinking that “all the bad ones are pretty uncommon these

      1. Your first link has a handy popup ad. Your second link has this:

        “Want to know how to choose the safest sunscreen?
        For a donation of $5, you can take EWG’s Guide to Safer Sunscreens to the store with you today!”

  2. Walking across a highway will not cause cars to hit you. There are many other factors involved, most of which are unknown. 

  3. I’m sorry to threadjack, but I gotta get this out there – I think I might have discovered a free, effective sunscreen.  The catch is it only works on me.

    With thin hair and a growing bald spot, I used to burn to lobster consistency within 15minutes of any sun exposure.  Then I went “paleo” on my scalp a few months ago (meaning, I wash my scalp every day with water, but no soap.) 

    And this isn’t a double-blind study or anything, but I haven’t gotten burned since.  YMMV, but I encourage you to try it!

    I have “Mad Men”, and scores of hippies, to thank.

  4. one actual effect of the use of sunscreen is the death of coral reefs. this is documented and the effect of the reflective particles deposited on the surface of coral and preventing coral from respiring and naturally benefiting from the normal full spectrum of solar energy it needs to be healthy. this is is huge problem anywhere there are thousands of bathers in the water at tropical beaches. 

      1. Fun fact, Australian sunscreen ratings cap out at SPF30+.

        Incidentally, Australian research has demonstrated a link between use of (SPF15+) sunscreen and decrease in incidence of melanoma, see abstract or full paper at

        According to our Cancer Council, this is on top of research demonstrating a decrease in rates of the most common form of carcinoma, but I couldn’t find a reasonable link to a paper for that.

  5. In 2005 I wrote a university paper about this. There was tons of misinformation out there, reviews claiming that sunscreen was helping for cancer in various areas, but when I followed the references it was all a lie.

    A sunscreen conspiracy.

    1. When you say that you wrote a university paper about this, do you mean a freshman English paper or a research paper for medical school, or somewhere in between?

      1. Would it matter? It doesn’t take much skill to read a paper, find the linked paper, and notice melanoma rates increasing rather than dropping as referenced.  Fair question;  unfortunately based your past comments I read everything you write with a tinge of douche :)

        A medical genetics course on cancer offered to seniors; I took it while in Computer Science.   A research paper for medical school.

        1. Would it matter? It doesn’t take much skill to read a paper, find the linked paper, and notice melanoma rates increasing rather than dropping as referenced.

          Yes, it would matter. There is all kinds of garbage written by people who have no idea how to interpret research data, are operating off political or corporate agendas or are just bugfuck crazy. Your ability to distinguish between good research and bad research is unknown, and a paper that you hand in to a med school professor would be judged quite differently than a freshman book report.

        2. Not to gang up on you, but even if this was for a senior medical genetics course, you could have received an F on the paper. Even if you received an A+, that’s not the same as having a peer-reviewed article in a scientific journal.

  6. If you die at age 65 from skin cancer, but you spent your entire life outside rather than cooped up in front of the TV not knowing you’ve sealed your fate, did you really “lose”?

    I’d like to go out the same way as Lister did – crashed his private jet at age 85 in to a mountain while trying to remove the bra from a college age coed  with his teeth – but living a blissfully ignorant life outside and in the sun is a close second.

    1. People always talk about ‘living large’, but the reality is that if you don’t take care of yourself, you spend about a decade in constant pain and unable to walk to the end of the block before you get to the dying part.

      1.  However even if you don’t “live large” you still end up with a decade of constant pain unable to walk before the end.   Assisted living facilities aren’t packed full of geriatric adventurers.

    2. No offense, but if you’re busy reading/posting comments to Boing Boing are you really living life to its fullest?

  7. Imo the “sunscreen scam” is going to be the  greatest health scandal of the 21st century, tobacco is NOTHING compared to this.
    UVA causes cancer and is not blocked by sunscreen
    UVB doesn’t cause cancer and is being blocked… and  the really scary thing is that UVB produces vitamin D, which is now slowly being recognized as the primary defence mechanism against cancer (basically white blood cells for cancer)
    add 2 and 2 and check out the latest research into vitamin D. then take a look at cancer incidence by geographical location and sunscreen use and then… get really, really mad.
    Basically, sunbathing is normal for humans. Whatever cellular damage happens due to UVA is repaired by vitamin D produced by UVB component of sunlight. And, of course, vitamin D prevents all other types of cancer as well. Even if the sunscreen blocks UVA as well, the vitamin D deficiency caused by blocking of UVB is quite enough to seriously screw up your natural cancer defenses. If I was an evil mastermind wishing to kill as many people as simply and innocuously as possible, I’d tell them to wear sunscreen (and invest heavily into medical “cancer industry”)

    1. Please post a copy of your degree so we can asses your credentials.. you seem so sure of things that you must be a recognised expert.

      1) UVA is blocked by some sunscreens.
      2) No one says to wear sunscreen at all times. Sunscreen is for use during extended sun exposure. A short period (minutes) of sun exposure every day is easily enough to get our vitamin D.
      This from the Cancer Council (who I trust more than you, sorry):
      During summer in the southern parts of Australia (for example Sydney, Melbourne, Canberra, Adelaide, Hobart and Perth), and all year round in the north (Brisbane and Darwin), most of us need a few minutes a day of sun exposure to an area of skin equivalent to your face, arms and hands. In winter in the southern parts of Australia, where UV radiation levels are below 3 all day, most of us need about two to three hours, spread over each week, to the face, arms, hands or equivalent area. People with naturally very dark skin need 3-6 times this amount.
      3) Sunbathing is not normal for humans. Sun exposure is normal. Laying in the baking sun on a beach for hours is not normal.

      IRT Marko Raos’s reply: That’s a lot of typing for a non-reply. Think what you want – there’s plenty of crackpot lunacy out there if you care to find it. Funny how you instruct me to check the facts, but don’t provide any links which I can follow to do so (I’d follow them, but probably still mock you). I provided a link and you just ignored it because it didn’t fit with your narrative. I’m sure the non-profit NGO I linked to, which tasks themselves with reducing the illness caused by cancer, is on the payroll of big pharma, or big.. sunscreeena or whoever in your theory is holding back the truth. That’s the only reason they would be contradicting your 4-whole-years of research, right?

      That’s cool if you wanna ignore information incompatible with your chosen beliefs but don’t be surprised when people laugh you off when you express your opinion. Oh, and go fuck yourself if you expect others to waste their time searching to prove your batty opinion. I trust science. You trust…. I don’t even know what. Your numbers are entirely meaningless without sourcing and your reply only stands to prove the tenuousness of your beliefs. Thanks for helping my argument.

      1. I get your drift but…

        #2… Whether right or wrong, I’ve heard many dermatologists recommend this.

        #3… I work in an office at a desk. Much of the world doesn’t. 8 hours in a open field with your shirt off is probably not uncommon for these folks. And, in an evolutionary context, more sun exposure than less is probably the norm. Labeling it “sunbathing” or not is a little beside the point.

        1. #2 “dermatologists”,  you mean peddlers of patented skin-care chemicals? Wear a hat, man. (Not a tin-foil one, a plain straw hat will do perfectly)

          #3 sorry i meant “normal sun exposure” rather than “sunbathing” My bad. However, D vitamin deficiency extends into other areas as well, the primary one being during winter months in areas away from the equator. Since vitamin D is stored primarily in fat tissue the whole “fat is bad” thing kinda goes to hell… And the fact that natural vitamin D is synthesized from…. cholesterol! Don’t eat eggs! Remember? And if you want to get really freaked out check out the research into vitamin D content of pig fat (aka lard) – free range vs basement grown. Again, clear corellation there, not geographical but temporal one from the 60’s onwards. As I said above, in two years the shitstorm is coming.

      2. I won’t bother to reply. Check the facts, open your eyes and I’ll see you in a couple of years. I’ve been following this story for the past 4 years, ever since my mother died of melanoma. It’s the shit. As I said, see you in a couple of years. The writing’s on the wall. The fact that boingboing published this article which challenges the “wear sunscreen” paradigm is one of the signs that the tide is changing. In two years you’lll have such a shitstorm you wouldn’t believe possible. “evil tobacco industry” is NOTHING compared to vitamin D/sunscreen/cancer industry combo. (400 ius as FDA’s reccommended daily level? a human with normal sunlight exposure generates 20 to 50 THOUSAND units per day!) If you thought people were pissed because of tobbacco death merchants you’ve seen NOTHING yet. I’m talking about death-profiteering at the very highest levels. It’s all out there, 100% legit and scientifically unchallengeable, published and recognized and validated… and yet totally ignored by mainstream media. And why? You tell me why. I used to laugh at “conspiracy theorists” until I came upon this stuff. But I won’t tell you anything. Everything is out there and “if you have eyes you should see.” The only thing i’d redact in my original post is to substitute “sunbathing” for “sun exposure.” Sorry, passion of the moment.

  8. Maggie I always trust that what you present on BB is as factually accurate as possible but it seems to me, going by first principles, it would stand to reason that minimising extra incidents of cell repair would also minimise the potential of one of those repairs going wrong and turning cancerous, no?

    Of course reason is not data, but for me it seems a whole lot more reasonable to assume sunburn leads to cancer than to assume there is no connection.

    -A fellow burnable whitey

  9. In this Fresh Air interview the person being interviewed also talked about how much sunscreen you have to use and it is a crazy amount. I usually just spritz but apparently when they test the sunscreens they cake it on really heavy.

  10. You know what works better than suncreen? Melanin. Human meloncyte production. There is a non FDA drug out there called Afelmelanotide (sp.).  I’ve used it to boost a-MSH production in my body as an experiment. It works like gangbusters but its too strong as it currently is produced.  In the future you will take a pill or take a shot to increase your pigment in order to protect your body from UV(A/B/C).  Just my opinion.

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