Does Sunscreen Cause Cancer? The Viral Claim, the Real Study, and What Your Sunscreen Actually Contains

"When a viral post tells you to stop protecting yourself from the sun, patients get hurt. But when the medical establishment tells you every chemical you put on your skin is perfectly safe — that's not honest either. The truth is in the middle, and you deserve to hear it."

— Dr Eugene Pretorius, Cancer SA Centurion

From Dr Eugene Pretorius

Patients have been sending me a viral post all week. It claims that a massive study has proven that sunscreen causes cancer.

The language is dramatic — "NUCLEAR BOMBSHELL", "BIG PHARMA SCAM", "dark secret EXPOSED".

As a doctor who has treated cancer patients for over 25 years, I cannot let this go unchallenged. But I'm also not going to do what most mainstream responses do — simply say "sunscreen is safe, trust the science, move along."

Because here's the thing: the viral claim is wrong about what the study shows. But the broader question — are all sunscreen ingredients safe? — has an answer that might surprise you.

I read the actual study. I looked at the raw data. And then I looked at what's actually inside the sunscreens people are putting on their skin every day.

Here is the full, honest picture.

The Viral Claim

A post going around social media, attributed to Nicolas Hulscher (MPH), claims:

"A massive, groundbreaking UK Biobank study tracking over 470,000+ PEOPLE has revealed the shocking, undeniable truth: frequent sunscreen use is directly linked to a staggering 292% HIGHER RISK of multiple skin cancers!"

It sounds terrifying. Parts of it are true — the study is real, the number does appear in the data, and the 470,000 figure is correct.

But the conclusion — that sunscreen causes cancer — is not what the study found. And the study's own researchers say so.

What Was This Study Actually About?

The study was published in November 2023 in Cancer Epidemiology, Biomarkers & Prevention — a respected journal. The researchers were at McGill University in Montreal.

But here's the important part: it was not a study about sunscreen.

It was a genetics study. The researchers wanted to find out which DNA repair genes — the genes your body uses to fix sun damage — make some people more likely to develop skin cancer than others.

Sun protection was one of 11 lifestyle factors they looked at. It was not the focus.

Nicolas Hulscher is not an author on this study. He took numbers from someone else's genetics paper and presented them as if they proved something the authors never claimed.

Why the Claim Falls Apart When You Look at the Method

The 292% number appears in the data. But how it was calculated changes everything. Here are three problems — and I'll explain each one so simply that a child could understand it.

Problem 1: They didn't account for anything else

The researchers looked at each factor on its own. When they looked at sun protection, they did not also account for how much time the person spent in the sun, what colour their skin was, whether they had been sunburned before, or whether they already had cancer.

Think of it this way: if you looked at data from a hospital, you'd find that people who take the most medicine are also the sickest. Does that mean medicine makes people sick? Of course not. Sick people take more medicine because they are sick.

Same thing here. People who spend a lot of time in the sun use more sunscreen. They also get more skin cancer. The sun is causing both things — the sunscreen use and the cancer. The sunscreen didn't cause the cancer.

Problem 2: The question wasn't even about sunscreen

The UK Biobank questionnaire asked:

"Do you wear sun protection (e.g. sunscreen lotion, hat) when you spend time outdoors in the summer?"

Notice: it says "sun protection" — which includes hats, long sleeves, staying in the shade, and sunscreen. The viral post says "sunscreen causes cancer," but the data doesn't separate sunscreen from wearing a hat. Someone who always wears a hat and someone who always applies SPF 50 gave the same answer.

Problem 3: People who already had cancer started using more sunscreen

Imagine someone diagnosed with skin cancer in 2018. Their doctor told them: "Wear sunscreen every single day." When the questionnaire asked about sun protection, they answered "always."

In the data, they appear as both a cancer patient and a frequent sunscreen user. But the cancer came first. The sunscreen was a response to the diagnosis — not the cause of it.

The study's own authors wrote that their data "does not account for changes in behaviour before and after disease diagnosis."

What did the study's researchers actually conclude?

The researchers at McGill University knew their data showed this paradox. Here is what they wrote in the actual paper:

"These findings demonstrate the importance of adequate and frequent sunscreen use and minimisation of exposure to UV light."

The people who collected this data, who built the model, who understood every limitation — concluded the exact opposite of the viral claim.

The Real Evidence: What Happens When You Actually Test Sunscreen?

If you want to truly know whether sunscreen prevents cancer, you can't just look at who uses sunscreen and who gets cancer — because too many other things get mixed in. You have to do what's called a randomised controlled trial: take a group of people, randomly split them in half, give one group sunscreen and the other nothing, and follow them for years.

This study has been done.

In 1992, researchers in Nambour, Australia enrolled 1,621 people. Half were randomly given free unlimited SPF 16 sunscreen and told to apply it daily. The other half continued their normal habits.

Because it was random, you couldn't choose which group you ended up in. Sun lovers, fair-skinned people, and people with prior skin problems were equally likely to end up in either group. Every confounding factor was balanced.

After 15 years:

• Daily sunscreen group: 11 new melanomas (3 invasive)
• Normal habits group: 22 new melanomas (11 invasive)

The daily sunscreen group had 50% fewer melanomas overall, and 73% fewer invasive melanomas.

This is the gold standard of medical evidence. Sunscreen, when used properly, prevents melanoma. That part of the science is settled.

But Here's the Honest Question Most People Are Really Asking

When patients ask me about the sunscreen post, they're not really asking "does sun protection prevent cancer?" Deep down, most people know that staying out of the sun and covering up prevents skin damage.

What they're actually asking is: "Are the chemicals in my sunscreen safe?"

And this is where the honest answer gets more interesting — because not all sunscreens are the same, and your body knows the difference between a natural mineral sitting on your skin and a synthetic chemical it was never designed to process.

Two Very Different Classes of Sunscreen

There are two fundamentally different types of sunscreen. They work differently, they interact with your body differently, and they have very different safety profiles.

Mineral sunscreens (the natural ones)

These contain zinc oxide or titanium dioxide — natural minerals that sit on top of your skin and physically reflect UV light away, like a mirror. They don't get absorbed into your body. Studies show they stay in the outermost dead layer of skin, with trace blood levels roughly 1/1,000th of the zinc already circulating naturally in your body.

These are the only two sunscreen ingredients the FDA classifies as GRASE — Generally Recognised as Safe and Effective. Out of all sunscreen ingredients on the market, only these two have enough data to be called safe.

Chemical sunscreens (the synthetic ones)

These contain laboratory-made chemicals like oxybenzone, octocrylene, homosalate, avobenzone, and octinoxate. Instead of sitting on your skin, they absorb into your skin, soak up UV light, and convert it to heat.

The problem is that they don't just stay in your skin. They pass through it and enter your bloodstream.

The Chemical Filters Worth Watching

This is not speculation. These are findings from the FDA's own studies and peer-reviewed research published in major journals.

Oxybenzone — the most studied, the most concerning

In 2019 and 2020, the FDA itself ran clinical studies on sunscreen absorption. They found that oxybenzone passed through the skin and into the bloodstream within hours of a single application, at levels far above the FDA's own safety threshold.

That threshold — 0.5 nanograms per millilitre — is not a "danger line." It is the level below which the FDA says no further testing is needed. Above it, they want more safety data. Oxybenzone blew past it on day one.

What else we know about oxybenzone:

• The European Chemicals Agency (ECHA) has officially classified it as an endocrine disruptor — meaning it interferes with your hormonal system
• It mimics oestrogen in laboratory studies
• It has been found in breast milk at concentrations exceeding 20 ng/mL — seven days after women stopped applying it
• It is banned in Hawaii because it damages coral reefs at extraordinarily low concentrations
• The EU has lowered the permitted concentration in sunscreens because their safety committee concluded it wasn't safe at the levels being used

Octocrylene — the one that turns into a carcinogen in the bottle

In 2021, researchers at Sorbonne University made a disturbing discovery. Octocrylene — a UV filter found in many popular sunscreens and anti-ageing creams — breaks down over time inside the bottle into benzophenone, a compound classified as a known carcinogen and endocrine disruptor.

They tested 15 commercial products from France and the United States. Every single one contained benzophenone. And the concentration increased as the product aged — meaning the sunscreen sitting in your bathroom cabinet right now may contain more benzophenone than when you bought it.

Homosalate — restricted in Europe in 2025

Homosalate has been shown in animal studies to disrupt thyroid hormone production and interfere with androgen and progesterone signalling. This isn't just a theory that regulators are ignoring — they acted on it.

As of 1 July 2025, the European Union restricted homosalate to a maximum of 7.34%, and only in face products — not body lotions or sprays. The EU's own scientific committee concluded homosalate is not safe as a UV filter at the concentrations of up to 10% that had been common, specifically because of its potential endocrine-disrupting properties. When a major regulator cuts the allowed amount by more than a quarter and bans it from body products, that tells you something.

Octinoxate — oestrogenic and thyroid concerns

Octinoxate (octyl methoxycinnamate) shows oestrogenic and anti-androgenic activity in laboratory studies, and affects thyroid function. It is also banned in Hawaii alongside oxybenzone for coral reef damage.

The FDA's own position on the chemical filters

As of today, the FDA classifies sunscreen ingredients into three groups:

• Safe (GRASE): Zinc oxide, titanium dioxide — only these two
• Unsafe: PABA, trolamine salicylate — banned
• Insufficient data to determine safety: Oxybenzone, avobenzone, octocrylene, homosalate, octisalate, octinoxate, and six others

Read that last category carefully. The FDA is not saying these chemicals are dangerous. It is saying they don't have enough data to say they are safe. After decades on the market, being applied to the skin of billions of people, the safety data simply hasn't been provided.

"Approved" is not the same as "safe"

This is the point I most want you to take away. A regulator approving a chemical is not the same as that chemical being proven safe. Approval is a floor — a snapshot of what was known at the time, filtered through data that industry itself often supplies. It is not a guarantee.

History proves this over and over. Every one of the chemical filters now being restricted or questioned — oxybenzone, octinoxate, homosalate — was once freely approved and considered perfectly fine. Nothing about the molecule changed. Our knowledge changed.

And here is the deeper principle behind how I think about this as an integrative doctor: your body was designed to recognise and process compounds that occur in nature. It has enzymes, transporters, and detox pathways for them. When you introduce a man-made molecule that does not exist in nature, you are asking your biochemistry to deal with something it was never built for. Sometimes that's fine. But often we simply do not yet know every pathway that molecule touches — which hormone receptor it nudges, which enzyme it blocks, what it becomes as it breaks down. The absence of proof of harm is not the same as proof of safety.

So my default is simple: the fewer novel synthetic chemicals I ask my skin to absorb, the better. When nature offers a tool that does the same job — a mineral your body already knows — that is where I start.

It's Not Just the UV Filter — the Carriers, Preservatives and Additives

When you put a chemical sunscreen on your skin, you're not just applying one UV filter. You're applying a cocktail of synthetic ingredients — and several of the "inactive" ones are worth knowing about, because your body has no natural machinery to break many of them down.

• Penetration enhancers — ingredients like propylene glycol and disodium EDTA are added to help the product spread and sink in. The problem: they don't just carry the sunscreen in, they can increase how deeply the chemical filters penetrate your skin and reach your bloodstream. You're actively helping the compounds you'd rather avoid get inside.
• Parabens — preservatives that have been shown to weakly mimic oestrogen, and have been detected in human blood and tissue.
• Synthetic "fragrance" — a single word on the label that can legally hide dozens of undisclosed chemicals, including phthalates (hormone-disrupting plasticisers) and common allergens. If you can't find out what's in it, that's reason enough to skip it.

One ingredient deserves a fairer hearing than it usually gets: retinyl palmitate (vitamin A), which you'll sometimes see on "avoid" lists. Here's the honest nuance — and it's a good example of the very principle this article is built on. Retinyl palmitate is a natural form of vitamin A: it is the exact form your own body uses to store vitamin A, and you take it in from food every day. A single government animal study once raised a question about vitamin A combined with intense UV light in hairless mice — but that finding has not been shown to translate to human skin, and dermatology reviews have concluded it does not cause skin cancer in people. Because it is a natural, body-recognised nutrient rather than a novel man-made chemical, it simply isn't in the same category of concern as the synthetic filters. It doesn't add sun protection, so it's not essential in a sunscreen — but it is not the red flag the internet made it out to be. That's the difference between something your body knows and something it doesn't.

Are the Minerals Themselves Safe? The Honest Answer on Nanoparticles

To be fair and complete, I have to address the one real question about mineral sunscreens: nanoparticles. To make zinc oxide and titanium dioxide rub in clear instead of leaving a white cast, manufacturers often grind them into ultra-fine "nano" particles. Is that safe?

Here the evidence is genuinely reassuring — with one caveat:

• On intact skin, they stay on the surface. The large majority of studies show nano zinc oxide and titanium dioxide remain in the outermost dead layer of skin (the stratum corneum) and hair follicles. They do not meaningfully pass into living tissue or the bloodstream. On current evidence, they are unlikely to cause harm applied to healthy skin.
• The real concern is breathing them in. The genuine risk from nanoparticles is inhalation — where fine particles reach the lungs and cause inflammation. That means spray and powder sunscreens are the ones to avoid, not creams and lotions.

So the natural-first, cautious approach is straightforward: choose a non-nano (or "micronized-free") mineral cream or lotion, never a spray or powder. Non-nano zinc oxide leaves a slight white sheen — that visible layer is precisely the point. It's sitting on top of your skin, doing its job as a physical mirror, exactly where you want it.

What About the "Better" New Filter Approved in 2026?

You may have seen headlines that in June 2026 the FDA approved bemotrizinol (also called Tinosorb S) — the first genuinely new sunscreen filter in the United States in 25 years. It's a chemical filter, but a smarter one: it's a very large molecule, so it's barely absorbed through the skin, it's highly photostable (it doesn't fall apart in sunlight the way octocrylene does), and it covers both UVA and UVB well. On paper, it looks far better than the old chemical filters.

I want to be honest and balanced: this is real progress, and it is almost certainly a better choice than oxybenzone or homosalate. If you or your family prefer a cosmetically elegant sunscreen that rubs in completely, bemotrizinol-based products are a reasonable option, and I won't pretend otherwise.

But hold it to the same standard as everything else on this page. "New" and "approved" are not the same as "proven safe over a lifetime." Bemotrizinol is still a man-made molecule that does not occur in nature. It has been studied for the things we currently know to look for — and it performs well on those. What we cannot yet know is what 20 or 30 years of daily, whole-body use reveals, or every subtle biochemical pathway it may touch. That's not a criticism of the molecule; it's simply the honest limit of new-chemical safety data. Remember: the filters we're now restricting were also "approved" once.

So I mention it so you're fully informed — but for my own patients, my default remains the mineral your body already recognises. When in doubt, choose what nature made.

How to Choose the Least Harmful Sunscreen — A Simple Guide

Here is my honest, practical advice — not as someone selling sunscreen (we don't sell any), but as a doctor who has spent 25 years treating cancer patients. Think of it as a hierarchy, from best to acceptable.

✅ Best choice: non-nano mineral

• Look for zinc oxide as the active ingredient — it's the only single ingredient that blocks both UVA and UVB, and your body recognises zinc as an essential mineral it needs to survive
• Titanium dioxide is also a safe mineral, though it covers less of the UVA range
• Choose non-nano where you can, in a cream or lotion — never a spray or powder
• Accept a slight white sheen — that's the mineral sitting on top of your skin, exactly where it should be

🟡 Acceptable if you want a clear finish: new-generation filter

• A bemotrizinol-based product is a reasonable, better-than-the-old-chemicals option — but it's still synthetic and new, so it wouldn't be my first choice

❌ Read the label and avoid

• Oxybenzone (benzophenone-3) — endocrine disruptor, absorbs into blood, banned in Hawaii
• Octinoxate — oestrogenic activity, banned in Hawaii
• Octocrylene — degrades into a carcinogen (benzophenone) inside the bottle over time
• Homosalate — hormonal concerns; the EU cut its allowed limit in 2025
• Added synthetic fragrance, parabens, and penetration enhancers — an ingredient list you can't understand is a reason to put it back on the shelf

The golden rule of labels

The shorter and more recognisable the ingredient list, the better. A good mineral sunscreen can have a remarkably simple formula. If the label reads like a chemistry exam, choose something else.

Sunscreen is one layer — not the only layer

• Apply generously — most people use far too little to get the protection on the label
• Reapply every two hours — and after swimming or sweating
• Wear a hat and protective clothing — especially in South Africa, where UV levels are among the highest in the world
• Seek shade in the midday sun — 10:00 to 14:00 is when UV is strongest
• Don't treat sunscreen as a licence to bake — applying SPF 50 and then spending six hours in the midday sun still leaves you worse off than staying in the shade

Protection From the Inside Out — the Natural Layer Most People Miss

Here is the part conventional advice almost never mentions: what you eat changes how your skin handles the sun. Your skin's defence against UV damage isn't only the layer you rub on the outside — it's also built from the antioxidants circulating inside you. This is real, published science, and it's the most natural sun protection there is.

Eat your sunscreen

• Lycopene (tomatoes) — in controlled studies, people eating tomato paste or tomato-derived lycopene for 10–12 weeks developed up to 40–48% less UV-induced skin redness than those who didn't. Cooked tomatoes, tomato paste, and watermelon are rich sources.
• Carotenoids (β-carotene, lutein) — from carrots, sweet potato, leafy greens and other brightly coloured plants; they accumulate in the skin and act as internal antioxidant filters.
• Green tea and cocoa polyphenols — reduce UV-driven inflammation and help protect the collagen that keeps skin from ageing.
• Omega-3 fatty acids — from oily fish, flax and walnuts; help calm the inflammatory response to UV.
• Vitamins C, D and E — classic antioxidant support for skin exposed to sunlight.

Two well-studied natural supplements

• Polypodium leucotomos (a fern extract, sold as Fernblock) — one of the most researched oral photoprotectants. In randomised, placebo-controlled trials it raises the amount of UV the skin can take before it burns, by neutralising the reactive oxygen species that sunlight generates. Taken orally, with a strong safety record.
• Astaxanthin — one of nature's most powerful antioxidants (from microalgae), shown in human studies to protect against UVA/UVB damage while improving skin hydration and elasticity.

Important: none of these replaces putting a physical barrier on your skin or staying out of harsh midday sun. They are a complement — an extra, internal layer that lowers the oxidative burden UV places on your body. But they are exactly the kind of natural, body-friendly protection that fits how I believe we should care for ourselves: working with the body's own chemistry, not against it.

One balancing word: sensible sunlight also has real benefits — most importantly vitamin D. The goal is never zero sun. It's smart sun: enough to thrive, protected in the least harmful way, without the burning that drives skin cancer.

A Special Note for Cancer Patients

If you are currently undergoing cancer treatment — including some of the therapies we use at Cancer SA — your skin is likely more sensitive to sunlight than normal. Many chemotherapy drugs, IV therapies, and even some supplements increase photosensitivity.

Sun protection during treatment is not optional. But given the hormonal concerns with chemical sunscreens, this is one more reason to choose mineral sunscreens during your treatment. Your body is already under enormous stress — the last thing it needs is to process synthetic endocrine disruptors through the skin on top of everything else.

Talk to your treating doctor about your specific needs.

Frequently Asked Questions

References

1. Jeremian, R., Xie, P., Fotovati, M., Lefrançois, P., & Litvinov, I.V. (2023). "Gene–Environment Analyses in a UK Biobank Skin Cancer Cohort Identifies Important SNPs in DNA Repair Genes." Cancer Epidemiology, Biomarkers & Prevention, 32(11), 1599–1607. PubMed Central
2. Green, A.C. et al. (2011). "Reduced Melanoma After Regular Sunscreen Use: Randomized Trial Follow-Up." Journal of Clinical Oncology, 29(3), 257–263. JCO
3. Matta, M.K. et al. (2020). "Effect of Sunscreen Application on Plasma Concentration of Sunscreen Active Ingredients." JAMA, 323(3), 256–267. (FDA absorption study) JAMA
4. Matta, M.K. et al. (2019). "Effect of Sunscreen Application Under Maximal Use Conditions on Plasma Concentration of Sunscreen Active Ingredients." JAMA, 321(21), 2082–2091. (FDA pilot study) JAMA
5. Downs, C.A. et al. (2021). "Benzophenone Accumulates over Time from the Degradation of Octocrylene in Commercial Sunscreen Products." Chemical Research in Toxicology. ACS Publications (Sorbonne octocrylene study)
6. European Chemicals Agency (ECHA). Classification of benzophenone-3 (oxybenzone) as an endocrine disruptor. ECHA decision
7. UK Biobank Data Field 2267: "Use of sun/uv protection." UK Biobank
8. European Commission (Regulation (EU) 2022/1176) / SCCS. Homosalate restricted to a maximum of 7.34% and permitted only in face products (excluding propellant sprays), effective 1 July 2025, on endocrine-disruption grounds. EU Homosalate Rule (July 2025)
9. US FDA, OTC Monograph Order OTC000039 (2026): bemotrizinol (Tinosorb S) determined GRASE as an over-the-counter sunscreen active ingredient — the first new US sunscreen filter in ~25 years; a large molecule with minimal systemic absorption. FDA OTC Monographs — Order OTC000039
10. "New Perspectives on Titanium Dioxide and Zinc Oxide as Inorganic UV Filters: Advances, Safety, Challenges, and Environmental Considerations." (2025). Cosmetics (MDPI), 12(2):77. MDPI Cosmetics. See also TGA (Australia), "Literature review on the safety of titanium dioxide and zinc oxide nanoparticles in sunscreens." TGA
11. National Toxicology Program (2012). "Photocarcinogenesis study of retinoic acid and retinyl palmitate in SKH-1 mice (Simulated Solar Light and Topical Application Study)." NTP Technical Report 568 — retinyl palmitate enhanced UV photocarcinogenicity in the mouse model. PubMed. (For the opposing dermatology view that this does not translate to human skin-cancer risk, see Wang SQ, Dusza SW, Lim HW. "Safety of retinyl palmitate in sunscreens: a critical analysis." J Am Acad Dermatol, 2010. PubMed.)
12. Aust O, Stahl W, Sies H, Tronnier H, Heinrich U. (2005). "Supplementation with tomato-based products increases lycopene, phytofluene, and phytoene levels in human serum and protects against UV-light-induced erythema." International Journal for Vitamin and Nutrition Research, 75(1):54–60. PubMed
13. "Effects of Eight-Week Supplementation Containing Red Orange and Polypodium leucotomos Extracts on UVB-Induced Skin Responses: A Randomized Double-Blind Placebo-Controlled Trial." (2025). Nutrients. PubMed Central
14. "Effectiveness of dietary supplements for skin photoaging in healthy adults: a systematic review and meta-analysis of randomized controlled trials." (2025). Frontiers in Medicine. Frontiers

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This article is for educational purposes and does not constitute medical advice. Always consult your treating doctor about sun protection during cancer treatment, and before starting any supplement — especially during active treatment, as some supplements can interact with therapy. The analysis above is based on publicly available peer-reviewed research, FDA clinical trials, EU regulatory opinions, and published nutrition studies. Cancer SA has no relationship with, and receives no funding from, any sunscreen, cosmetic, or supplement manufacturer. We do not sell sunscreen products.