Does sunscreen cause cancer?
Like almost any topic in the field of health and wellness, it seems there is a tangled web of research and opinions when it comes to cancer, sun exposure and sunscreen ingredients.
Should we wear SPF 50 sunscreen for our walk from the house to the mailbox, or should we shun all sunscreens in our quest to increase our Vitamin D levels as much as possible? Do we buy sun protective clothing to safeguard every inch of our skin from the damaging UV rays, or should the real cause of our cancer fears be the sunscreen ingredients themselves?
When CNN broke the latest research on sunscreen in 2019 showing that YES, active ingredients in most sunscreens DO get into the bloodstream within just a day, the American community went hog wild sharing it.
But CNN of course spent more than half the article reminding us to wear sunscreen, wear it daily, and don’t change a single habit until science has had time to prove that what we’re slathering on our children multiple times a day is killing them slowly.
For my family, I choose not to be guinea pigs. I’ve been saying since 2010 that we need to run away from conventional chemical sunscreens, and I stand by that even more firmly today!
Since we now know that sunscreen actives do enter the bloodstream (thank you, science, for telling all of us through a tiny study of 24 people what those in the natural health world have known by common sense for decades), we can start to ask bigger questions — like what does it do in there?
Could sunscreen even cause the cancer we’re trying to avoid by wearing it??
How Sunscreen is Harmful to Humans
As usual, I’m going to seek the balance on this controversial topic and try to share with you some brief synopses of research on the issue. I am grateful for the direction EWG offers in their yearly Sunscreen Guides but realize that multiple sources are necessary, especially when I read articles like this one questioning EWG’s scientific validity. In spite of the rebuttal, I think EWG does a great job organizing a wealth of information.
The ultimate questions for any suncream is: Does it protect from both UVA (cancer causing) and UVB (skin damaging/burning) rays?
Look for terms like “broad spectrum” coverage for starters, and then you need to learn about UVA protection, which only comes from active ingredients avobenzone, zinc oxide and titanium dioxide. All sunscreens will protect from UVB rays because you’d notice if it wasn’t working – you’d be sunburned! [RELATED: Read why Avobenzone is a terrible choice for sunscreen!]
Notably, in 2011 the FDA banned the use of the term “sunblock” on sunscreen products.
How Chemical Sunscreen Works
“Sunscreens absorb UV energy and have to be absorbed into the upper layer of skin to really get up to full speed,” says Darrell Rigel, clinical professor of dermatology at New York University Langone Medical Center. (source)
A chemical reaction takes place between the sunscreen ingredients and the UV rays to “screen” your body from most of the effects of the sun. That’s why the instructions on the sunscreen bottles say to put it on 20 minutes before being exposed to the sun. It needs that time to sink in to your skin before its full SPF is realized. (1, 2, 3)
Because the active ingredients in chemical sunscreen don’t provide broad spectrum coverage alone, there must be a proper balance of multiple actives to offer balanced, safe coverage.
I use the term “safe” loosely there – safe from sunburn, but because the chemical constituents also degrade in the sunlight, they’re really not safe. More below…
How Mineral Sunscreen Works
Mineral active ingredients in sunscreen, on the other hand, are called a “physical” block rather than chemical. They sit on the surface of your skin rather than being absorbed into it. Most sources say that sunblocks “reflect and scatter UV light.” (1, 2, 3, 4 and many more)
On the other hand, the founder of Kabana, a biochemist from Stanford, disagrees with that explanation and claims instead:
“Zinc oxide has a broader UV absorption profile than titanium dioxide, which is noteworthy, because much misinformation populates the media about how these chemicals protect us – they do NOT reflect and scatter in the UV spectrum – rather zinc oxide absorbs UV and does so very effectively. The media (and ‘experts’ alike) need to investigate the physical chemistry of these compounds, rather than assume they reflect UV light because they look white in the visible spectrum. They do reflect in the visible, but would look black in the UV.” (source)
Either way, sunscreens use minerals that sit on the surface of the skin (usually zinc oxide and titanium dioxide) rather than chemicals that sink into the skin to protect one from the sun. Mineral sunscreens begin working right away on both UVA and UVB rays, so there’s no need to apply 20 minutes before sun exposure.
Here’s a GREAT interview with Erik Kreider, founder of Kabana. He covers all the science geek information and research about sun safety and the hazards of petrochemical sunscreens. I learned a lot!!
What is a Sunburn?
What exactly are we trying to protect ourselves from when we use sunscreen, anyway?
According to this source from a dermatologist: Ultraviolet rays of sun penetrate the skin and cause damage to the skin.
Inflammation and redness is a first level sunburn. Blistering means deeper damage to the skin. Tanned skin is superficially damaged skin. Tanning is the skin’s way of trying to protect the skin from damage.
What Does SPF Mean?
Every person’s skin has a certain tolerance for sun, and most people believe SPF (Sun Protection Factor) multiplies that tolerance. In other words, if you could spend 15 minutes in the sun without getting burned, applying the appropriate amount of an SPF 15 product would allow you spend 15 times 15 minutes in the sun. This is not actually 100% accurate about how SPF protects!!!
Another way of describing SPF is to say that the sunscreen absorbs UV rays at a percentage based on the SPF. For example, that SPF 15 sunscreen would allow your skin to absorb 1/15 th of the UV rays that it would if you weren’t wearing any protection. That’s about 6.7% of the rays coming through your sunscreen.
Here’s where it gets interesting. Using that formula, an SPF of 45 allows your skin to absorb 2.2% of the UV rays. Increasing the SPF three times only increased the protection by 4.5%. (1, 2) Some use that data to claim that SPF 15 is really all you’ll need, since higher SPFs don’t add much protection at all. This doc at WebMD says anything over SPF 45 is “silly” and recommends SPF 30 to patients.
Often studies show that those who use a higher SPF are more likely to get melanoma (skin cancer), possibly because they’re tricked into thinking they’re safe from the sun and stay out longer. In 2011 the FDA was considering banning SPFs over 50 because they can feel so misleading, but they didn’t go through with it.
It’s vitally important to note that SPF only applies to UVB rays, the burning rays of the sun. All the invisible damage from UVA and UVC rays may still be coming through your SPF 5,000 tube. Good thing zinc oxide protects from both all by itself!
All Sunscreens Release Free Radicals
The sun is said to cause cancer because it forms free radicals in the skin. Sunscreens help protect our skin (to an extent) from that radiation, but in the process they also form free radicals, because all the energy from the sun has to go somewhere.
The trick is to block more free radicals than the sun cream creates. Many sunscreens include natural antioxidants like Vitamin E or green tea to combat the formation of free radicals in the skin.
The Risks of Chemical Sunscreens
Since chemically-based sunscreens have to be absorbed into your skin just to start working, they have one strike against them already just for entering your system instead of sitting on the surface. Some of the potential health risks of chemical sunscreens include:
- Hormone disruption; mimics estrogen and raises risk of breast cancer (theoretical but frightening) 1, 2
- Allergic reactions
- Bioaccumulation in tissue and organs (found in 97% of Americans’ bloodstreams!)2
- Also found in mother’s milk, demonstrating its reach even to the unborn
- Oxybenzone is pegged for lowering thyroid hormone (source)
- Shaving may increase the absorption of the chemicals (source)
- Failure to biodegrade in the environment 3
Oxybenzone is the chemical ingredient with the most fingers pointing at it; that’s the one found in 97% of Americans. If I was only avoiding one ingredient, Oxybenzone would probably be the winner, especially for children, whose small bodies make them especially susceptible to endocrine disruptors. Hawaii agrees for the sake of the coral reefs!
Those free radicals that form when the sun’s rays touch the sunscreen are ironic, don’t you think, since you can’t exactly avoid that situation, or you wouldn’t need sunscreen in the first place. Free radicals are cancer-causing, but here’s the catch: It’s thought that both the sunscreen and the sun must penetrate deeper into the skin in order for the problems to happen.
If you reapply, the new sunscreen will, in theory, block the sun afresh and stop its path to the already well-absorbed sunscreen. If you don’t reapply, you may just be inviting skin cancer to roost in your skin. Applying a chemical sunscreen one time, particularly one with oxybenzone, and forgetting to reapply when still in the sun may have worse consequences than not applying any sun protection at all.
Risks of Mineral Sunblocks: Nano vs. Micronized Particles
As soon as you learn to look for words like “zinc oxide” and “titanium dioxide” on your sunscreen (sunblock!) bottles, another layer reveals itself. Apparently smaller sized pieces of the minerals rub in more effectively (but also change the way the UVA and UVB radiation is screened out). For aesthetic reasons, many sunscreens therefore use “nano particles” of both zinc oxide and titanium dioxide.
The smaller the particle, unfortunately, the more likely it is that it is absorbed into the skin, where it could cause unknown problems, including…what else? Cancer. 1, 2, 3 The nano particles may also be more hazardous to the environment and even if swallowed inadvertently while swimming.
This review of sunscreening agents from the Journal of Clinical and Aesthetic Dermatology states:
“Studies have shown that nanoparticles of these two compounds [zinc oxide and titanium dioxide] cause cytotoxicity, genotoxicity, and potential photocarcinogenecity.”
That article is a great overall scholarly summary of a ton of sunscreen information and research, if your science geek brain wants to go deeper.
You might also see the term “micronized” on a sunblock using zinc oxide or titanium dioxide. This is a smaller form of the minerals, but not as small as “nano”. If the ingredients weren’t “micronized” – simply the process of grinding them smaller – they would be gritty like sand, rather ineffective at protecting your skin, and pure opaque white if it was possible to apply correctly. Micronized minerals are not small enough to get through the cell walls and are nothing to worry about.
Not all sunscreens disclose on the labels whether they use nano or micronized minerals. A good rule of thumb: If your zinc or titanium sunscreen goes on clear it is nanosized.
Here is some scholarly research worth reading if you really want to know more: A review of the scientific literature on the safety of nanoparticulate titanium dioxide or zinc oxide in sunscreens
Is Zinc Oxide Better Than Titanium Dioxide?
This study shows that zinc oxide is far better at blocking UVA than titanium dioxide, important for broad spectrum coverage, and The Skin Cancer Foundation discusses how both zinc and titanium dioxide are broad spectrum but zinc is more effective.
This study from 1997 demonstrated that microfine zinc oxide is broad spectrum and a safe and effective sunscreen.
Here are some studies that demonstrate that titanium dioxide does not penetrate the skin: 1, 2, 3 However, here’s a great interview with sunscreen expert Erik Kreider in which he explains (around the 25-minute mark) that titanium dioxide is still not as preferable as zinc oxide because:
- Zinc oxide has the best UV absorption profile
- Zinc is a critical mineral nutrient and even in vitamins (whereas titanium dioxide is a heavy metal)
- Zinc oxide is the only active ingredient the FDA approves for babies – Zinc oxide is the active ingredient in many diaper rash crèmes, which is a pretty clear indication that it’s gentle and safe for even the most sensitive skin.
- Zinc oxide holds onto its electrons more tightly (and therefore should generate fewer free radicals when exposed to the radiation of the sun)
I am not opposed to or scared of titanium dioxide, but when I am looking at optimal ingredients, I prefer zinc only.
Zinc oxide is also the only active sunscreen ingredient approved by the FDA for infants under six months, which is a striking fact.
Zinc oxide is a better sunscreen ingredient, as it offers the best UVA protection of all current sunscreen chemicals, and titanium dioxide is second best. (source) I don’t know that I’d avoid titanium dioxide with as much vehemence as I avoid oxybenzone, for example, but pure zinc oxide sunblocks are probably the best choice.
Too much to look through right now?
I organized alllll the sunscreens we reviewed in their recommendation category – one page at-a-glance to find out what is safe to buy AND works! Print it or save to your phone for reference!
The guide also includes answers to questions people ask me all the time:
- Which brand rubs in the clearest?
- What’s the best for all day outdoor sports?
- How do I save money on natural sunscreens?
- What looks good on ladies’ faces?
- Is there an option that is FAST to apply to wiggly kids?
I’ll send a copy to your email so you can see it right away and find it again later!