Skin cancer is by far the most common type of cancer in the US and worldwide. At least one in five people will develop skin cancer by the age of seventy. The deadliest type of skin cancer is invasive melanoma, which accounts for only 1% of all skin cancer cases but most of the deaths. [1]
Most skin cancers are associated with exposure to sunlight, specifically ultraviolet radiation, and are potentially preventable. As explained in a recent article, sunscreens protect against ultraviolet radiation through both chemical and physical filters. One study in Australia showed that the incidence of melanoma was reduced by half for people who applied sunscreen daily versus those who only occasionally used it.
Longstanding work has been underway to increase access to effective sunscreen products in the US. When the Sunscreen Innovation Act passed in 2014, Senator Jack Reed, who authored the bill, said,
“[It] will help ensure US consumers have access to the safest, most effective sunscreens available.”
Requiring that these products be tested on animals undermines this objective.
Animal testing
The idea that animal testing is a necessary evil where the benefits to human health far outweigh ethical and other concerns has been disputed in the last several decades. A 2007 review examined the outcomes of treating several diseases, including osteoporosis and stroke, as they transitioned from animal to human (clinical) studies. The results were only in accordance half the time; in other words, animal studies were no more likely to predict benefits in humans than flipping a coin.
In 2007, the National Academy of Sciences called for reducing animal testing and recommended using new technologies that could eventually eliminate the need for animal testing. In my article, Light at the end of the testing tunnel, I discussed alternatives to animal testing that have gained acceptance in the broad scientific community and how the FDA is seriously looking at ways to reduce and replace animal testing with tests more relevant to humans.
I was seriously overly optimistic. With its proposed sunscreen order, the FDA has taken a step backward and requires time-consuming and expensive animal testing on sunscreen ingredients.
What is the FDA proposal?
In the US, the FDA regulates sunscreen products with an SPF of >15 as over-the-counter drugs. The FDA regulations consider whether an ingredient is “generally recognized as safe and effective (GRASE)”; if they are, no further testing is needed in humans or animals.
The FDA sunscreen proposal lists only zinc oxide and titanium dioxide, ingredients in “mineral sunscreens,” as GRASE, requiring no animal testing. However, these mineral sunscreens are often unappealing for people with darker skin tones because they can leave white streaks on the skin. The FDA has determined that para-aminobenzene (PABA) and trolamine salicylate are not GRASE. However, these ingredients are no longer used in sunscreen in the US, and this determination will have no practical significance.
For the final twelve ingredients [2], the FDA says that while they are not considered unsafe, they are “requesting additional information on these ingredients so that we can evaluate their GRASE status in light of changed conditions, including substantially increased sunscreen usage and exposure…”
This information comes from tests of developmental and reproductive toxicity tests and carcinogenicity, exposing many hundreds of animals per test to an ingredient before they are killed. A 2023 study estimated that 65,341 rats and mice were used in 109 carcinogenicity studies conducted for new drug applications to the FDA from 2015 to 2019.
Sunscreen ingredients can be tested using modern methods, which are more accurate, faster, and less expensive than outdated animal studies. A group of sunscreen manufacturers repeatedly proposed a plan to the FDA, supplementing information gathered from decades of sunscreen use by millions of people with an innovative non-animal testing plan. The proposed alternative can provide biologically relevant information applicable to mechanisms of toxicity in humans by using strategies such as analyzing skin absorption, gene expression, and cellular changes in human-derived cells. The FDA failed to approve this alternative approach.
The proposed sunscreen order runs contrary to the FDA’s 2017 Predictive Toxicology Roadmap and the intention of Congress, which has acknowledged that animal tests provide limited predictivity of human health outcomes, and that modern, cruelty-free testing methods be used. The FDA’s peer-reviewed scientific publications document drawbacks inherent in carcinogenicity testing on animals, recognizing that “the results are frequently positive for tumors and can be irrelevant to human cancer risk.” Animal carcinogenicity studies take more than two years to complete, and while speed is not the only factor, getting sunscreen products that prevent skin cancer to market promptly is crucial.
FDA experts have collaborated with international regulatory experts for years to develop guidance to assess carcinogenicity without defaulting to a lifetime test on animals. In a consensus statement from an Organization for Economic Co-operation and Development expert group, the FDA and other organizations note,
“It is now well recognized by the scientific and regulatory community that the conventional approach to carcinogenicity testing, particularly the use of the rodent cancer bioassay … has many limitations regarding reliability and relevance.”
This has ramifications beyond the US market. The European Union (EU) banned testing cosmetics, including sunscreens, on animals, and the European Commission has asked the FDA to clarify the thought process behind its newly required tests and has noted in comments to the agency that the sunscreen ingredients in question have a long history of safe use in the US and often, internationally. It adds that comprehensive toxicological safety reports have already led to the approval of most of these ingredients in Europe and other countries, pointing out that the FDA is blocking access to high-performing sunscreen ingredients in the US.
The FDA should apply the most reliable and human-relevant strategies available to evaluate sunscreens—including using existing safety data, ongoing clinical and consumer safety assessment, and non-animal testing methods—instead of insisting that companies conduct decades-old animal tests that have been shown to poorly translate to human health outcomes. The FDA should follow its own directives, but sadly, it looks like it is falling back into old habits, leading to out-of-date animal testing, slowing ingredients to the market, and ultimately preventing timely access to products able to prevent skin cancer.
[1] An estimated 200,340 cases of melanoma will be diagnosed in the US in 2024. Roughly half noninvasive in situ cases. 99% of melanomas are survived, but it is estimated that 8,290 people will die of melanoma in 2024. The vast majority of melanomas are caused by the sun. One UK study found that about 86 percent of melanomas can be attributed to exposure to ultraviolet (UV) radiation from the sun.
[2] Cinoxate, Dioxybenzone, Ensulizole, Homosalate, Meradimate, Octinoxate, Octisalate, Octocrylene, Padimate O, Sulisobenzone, Oxybenzone, and Avobenzone
Katherine Groff, MS, is a senior scientist in the Regulatory Toxicology Department at People for the Ethical Treatment of Animals, with more than 15 years of experience on animal and environmental topics.
