Does Sunscreen Prevent Skin Cancer?

Cynthia Bailey, MD|October 14, 2011

Hot off the press! The answer is.... NOT ENTIRELY, and the reason applies 365 days a year! Just reported in the Journal of Investigative Dermatology, UVA1 is more cancer causing than we thought.  UVA1 is the hardest part of the sun's UV rays to block with sunscreen.  It's different from the sunburn ray UVB, and even different from UVA2 (which falls between UVA1 and UVB). You've heard that the sun causes skin cancers.  You also occasionally hear that before 10 or after 3pm, and during the non-summer months,  the sun is less dangerous.  You've probably noticed that the sun feels less intense during these times and you might let your guard down. Well, the sunburn ray UVB is softer then, but UVA is out with the same intensity as always. In fact, all day, all year UVA is equally intense; sun-up to sun-down, equatorial location or north pole, summer or winter it doesn't change. This new study gives you more reason to want UVA rays off of your skin. The investigators found mutated DNA (thymine dimers)  in the deepest parts of the top epidermal layer of the skin after UVA1 exposure. Those mutations are how skin cancers start.

We already knew that UVA exposure causes free radical damage to skin leading to wrinkles, skin thinning, and generally accelerated skin aging. UVA exposure has also been correlated with an increased risk of developing the type of skin cancer called melanoma, but the full story between UVA exposure and skin cancer has had some gaps.  This new study is part of filling in those gaps. What you probably don't know is that sunscreens aren't all that great at protecting your skin from this UVA1. It's why sunscreens are controversial.  They keep the UVB off pretty well, slowing your development of a sunburn, which allows you to stay in the sun longer.......getting more UVA1.  In the US the only sunscreens that we have which I think block UVA1 well are the micronized zinc oxide sunscreens.  Even with the micronized zinc products though there is huge product variability in my experience.  That’s why I only recommend Solbar Zinc, Citrix and Glycolix Elite Sunscreens (see below).  I’ve watched these protect my patients for years and trust them.

What it means for you?

  1. Your really do need to keep the sun off your skin year round.
  2. Sunscreens alone aren't good enough.  When you’re planning to be out in that sun for a long period of time you need clothing, broad brimmed hats and shade for sun protection too.

This new study shows that the DNA damage that we associate with skin cancer formation is evident deep in the skin from UVA exposure too - the sun may not feel very harmful when you're getting mostly UVA rays, but it is!  This is big news and most definitely should dissuade you from letting your guard down just because the sun feels softer during non-peak UVB hours.  Remember, UVA comes through clouds and most windows too.

The Bottom Line: Don’t put your zinc oxide sunscreen away after summer or just because you don’t feel the sun burning your skin.  The sun is still causing damage - if wrinkles aren't enough motivation, how about skin cancer surgery? Remember to use clothing, full brim hats and shade to keep the UVA off of your skin too. Don't be fooled by windows or clouds, UVA gets through these! I’ve watched UVA damage play out on my patient's skin for years and I've built the right tools to help keep them as safe as possible.  Frankly, we all need UVA protection year round and I've worked hard to figure out the best tricks:

Dermatologist's 'turnkey' and patient proven sun protection solutions

Click here for my SunSavvy Ultimate Sun Protection Kit

Click here for everyday full brim sun hats

Got most of what you need and just need an individual product to fill in the gap?

Click here to see my individual sun protection products.

Reference: UVA1 Induces Cyclobutane Pyrimidine Dimers but Not 6-4 Photoproducts in Human Skin In Vivo, Angela Tewari, Robert P Sarkany and Antony R Young,  Journal of Investigative Dermatology , (6 October 2011) | doi:10.1038/jid.2011.283 Photo: Thanks and Gratitude to Patrick Hoesley

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