Do Sunscreens Actually Stop Skin Cancer? Two Toxicologists Say the Evidence Is Missing

The organic chemical filters in roughly two thirds of Australian sunscreens were never proven to prevent skin cancer, a 2021 review argues. Octocrylene appears in 600 of 924 Australian sunscreen products (64.9%), and the authors say none of the long-approved organic filters has the human evidence to back the cancer-prevention promise on the label.

DiNardo JC, Downs CA (2021) Failure to Protect: Do Sunscreens Prevent Skin Cancer in Humans? Toxicology: Open Access 7: 1000157.

In plain language

Most people buy sunscreen for one reason: to avoid skin cancer. This 2021 review article asks a blunt question. Do the chemical filters used in most sunscreens actually deliver on that promise?

The two authors, a retired toxicologist and an environmental laboratory director, went back through the published literature from 1973 to 2020. Their answer is uncomfortable. They argue that stopping sunburn is not the same as stopping skin cancer, and that the human evidence linking organic chemical filters to cancer prevention is thin to absent.

This is a review and opinion piece, not a new laboratory study. The authors did not run their own experiments. They gathered and interpreted what others had published, then drew a strong conclusion from it. That matters for how much weight to give it. But the regulatory facts they cite, especially from the United States Food and Drug Administration (FDA) and the International Agency for Research on Cancer (IARC), are real and checkable.

What the authors set out to examine

The paper is built around one claim that appears on sunscreen labels worldwide: that regular use helps reduce the risk of skin cancer. The authors trace this claim back to the 1978 FDA sunscreen monograph, the regulatory document that approved most organic filters still used today.

They are scathing about the quality of the evidence behind that original approval. They write that "The data and claims stated in the 1978 FDA Sunscreen monograph were unsubstantiated or misleading, as well as arguably frivolous." Approval at the time, they note, rested largely on basic irritation testing and short-wave ultraviolet (UVB) measurement, with very little understood about long-wave ultraviolet (UVA) and its role in skin cancer.

What they found in the literature

The authors separate two ideas that are often blurred together. Preventing sunburn is one thing. Preventing skin cancer is another.

On this point they quote IARC’s international evaluation directly. IARC concluded "the topical use of sunscreens reduces the risk of sunburn in humans and that sunscreens probably prevent squamous-cell carcinoma of the skin when used mainly during unintentional sun exposure. No conclusion can be drawn about the cancer-preventive activity of topical use of sunscreens against basal-cell carcinoma and cutaneous melanoma."

That IARC line is worth reading twice, because it cuts both ways. It credits sunscreens with reducing sunburn and probably reducing one type of skin cancer. It also says the evidence does not allow any conclusion about the two cancers people fear most, basal-cell carcinoma and melanoma. The authors lean hard on that second half.

They also point to the limits of the human trial evidence. Reviewing the prospective human studies, one set of authors they cite was driven to ask "Could it be that the nearly universal recommendation of dermatologists and professional societies to use sunscreen to prevent skin cancer is unfounded?"

The concerns, in the authors’ own words

The heart of the paper is a set of concerns about what chemical filters may be doing beyond simply blocking a sunburn.

The authors argue that suppressing sunburn can mask damage rather than prevent it. As they put it, "the subversion of sunburn by sunscreen use is not free of the unseen consequences that can lead to the future development of skin cancers and toxicities."

They name specific filters in this context. According to the paper, the actives "oxybenzone, octocrylene, octinoxate, PABA, and the European 4-methylbenzyliden camphor have been reported to induce free radicals" linked to a range of adverse effects. Octocrylene, one of the most common filters in Australian sunscreens, is named directly here.

On the broader safety picture, they quote the FDA’s own assessment, that the "public record does not support the safety of these chemicals." They note this is why the FDA moved organic actives out of the Generally Recognized As Safe and Effective (GRASE) category, declaring two of them not safe for human use and requiring more data on the remaining twelve.

The FDA’s specific reasoning, as quoted in the paper, focuses on absorption. The agency noted that "oxybenzone is absorbed through the skin to a greater extent than previously understood and can lead to significant systemic exposure," along with data showing "the presence of oxybenzone in human breast milk, amniotic fluid, urine, and blood plasma." The paper adds the FDA’s blunt summary that "Nearly all of these sunscreen active ingredients also have limited or no data characterizing their absorption."

The authors close on a stark count. They report that "400,159 deaths have occurred from malignant skin cancers between 1975 - 2017 representing a 54% increase," adjusting for population growth, since the major push to use sunscreens began.

The caveats the authors keep in view

A fair reading has to hold the reassuring evidence alongside the alarming claims, because the paper itself does.

IARC did credit sunscreens with reducing sunburn and "probably" preventing squamous-cell carcinoma during unintentional exposure. The "no conclusion can be drawn" finding on melanoma and basal-cell carcinoma is exactly that, an absence of proof either way, not proof of harm.

The mouse data the authors reproduce (from a separate 2020 study by Bode and Roh) is also more mixed than the headline suggests. In those experiments several organic filters, including octisalate, homosalate and octocrylene combinations, did reduce tumour measures. Zinc oxide performed best, but octocrylene combinations were among the stronger organic performers. The authors use this to argue mineral filters are superior, which is a reasonable reading, but it is not the same as showing the organic filters did nothing.

It is also worth being clear about what kind of document this is. It is a review with a thesis, published in an open-access toxicology journal. The authors are arguing a case, not reporting a neutral survey. Readers can weigh the regulatory facts (which are solid) separately from the interpretation (which is contested).

What the authors recommend

The authors do not tell people to abandon sun protection. Their conclusion is that "sunscreens do not prevent skin cancers associated with intentional sun exposure," and that, given current safety questions, "it would appear that the risks associated are outweighed by the lack of benefits observed."

Their practical advice leans on physical protection first: shade, clothing, a broad-brimmed hat, sunglasses, and avoiding peak hours. Where a sunscreen is wanted, they recommend consumers "use a non-nano particle-sized mineral-based zinc oxide or titanium dioxide sunscreen, which are currently considered safe and effective for human use."

How common are these filters in Australian sunscreens?

The filters the authors single out are not fringe ingredients here. Across 924 therapeutic sunscreen products listed on the Australian Register of Therapeutic Goods (ARTG), the organic chemical filters dominate the market.

Octocrylene, named directly in the paper’s free-radical discussion, appears in 600 products (64.9%). Octisalate (octyl salicylate) appears in 411 (44.5%) and homosalate in 410 (44.4%). Avobenzone, the most common filter of all, is in 641 products (69.4%). By contrast the two mineral filters the authors recommend are far less common: zinc oxide in 243 products (26.3%) and titanium dioxide in 47 (5.1%).

So the great majority of sunscreens Australians can buy rely on exactly the class of filters this paper questions, and only a minority use the mineral filters the authors favour.

Beyond the paper (regulatory context)

In Australia, all of these organic filters remain approved by the Therapeutic Goods Administration (TGA), which regulates sunscreens as therapeutic goods. The FDA position the paper describes (organic actives requiring more safety data to confirm GRASE status) reflects a 2019 proposed rule in the United States and is a regulatory status question, not a finding that the filters cause cancer. Zinc oxide and titanium dioxide are the two filters the FDA has proposed as GRASE. The European Union permits all of these organic filters with specific concentration limits.

Common questions

Does this paper prove sunscreen does not work?

No. It argues the human evidence for cancer prevention is weak or missing, which is a different claim. The authors and IARC both accept sunscreens reduce sunburn, and IARC says they probably reduce one type of skin cancer. The honest summary is that the evidence is incomplete, not that protection has been disproven.

Is this a clinical trial or a laboratory study?

Neither. It is a review and opinion article. The authors gathered existing published work and argued a case from it. The regulatory facts they cite are verifiable; the overall conclusion is their interpretation and is contested by many dermatology bodies.

Why do the authors keep returning to oxybenzone?

Because the FDA’s own absorption concerns centre on it. The paper quotes FDA data on oxybenzone reaching breast milk, urine, blood and amniotic fluid. Octocrylene is named alongside it in the free-radical discussion, which is why this paper is relevant to the most common Australian filters.

What do the authors suggest using instead?

Physical protection first (shade, clothing, hats), and where a sunscreen is used, a non-nano mineral product based on zinc oxide or titanium dioxide.

Should I stop wearing sunscreen after reading this?

The authors do not say that. They argue for better protection, not none. Skin cancer risk from sun exposure is real, and stopping all protection is not what the paper recommends. The takeaway they push is to favour physical cover and mineral filters, not to go unprotected.

About the authors

DiNardo: MSc Toxicology (St John's), 30+ years in cosmetics, former VP R&D at Revlon-Almay, CSO-Emeritus at Pharma Cosmetix, published across multiple toxicology areas, co-author of reference texts, regular sunscreen-regulation speaker.

Downs: Executive Director of Haereticus Environmental Laboratory, forensic ecotoxicologist known for the oxybenzone-coral research behind several reef bans, plus the octocrylene-to-benzophenone degradation work.

 Funding and competing interests: The paper is published as an open-access article under a Creative Commons Attribution License. The authors declared no competing financial interests in the publication.

Source

DiNardo JC, Downs CA (2021) Failure to Protect: Do Sunscreens Prevent Skin Cancer in Humans? Toxicology: Open Access 7: 1000157.