Evidence doesn’t show sunscreen increases cancer risk

A Facebook post makes a number of claims about sunscreen ingredients and potential health issues. The post concludes by summarising two reasons that “you should avoid sunscreen”. It says that it causes “endocrine disruption” and “increases the risk of skin cancer”. While studies have been done on these topics, neither of these claims are borne out in the evidence.

Bad information about health can cause harm if people make decisions based on it. We have previously written about social media posts that contain false information which may discourage people from using sunscreen and other sun protection.

Cancer risk 

Effective sunscreen should block UV rays—both UVA and UVB—from damaging the skin. Excessive UV exposure can cause sunburn, and DNA damage that can increase the risk of skin cancer in the future. 

The post says that “many recent studies have found that [...] sunblocks [...] actually increase the risk of developing melanoma”.

Skin cancer takes a long time to develop which can make research in the area more difficult. It also has a lot of contributing factors that can be hard to control for and this also complicates research.

But studies with follow up over decades have shown reduced rates of cancer with sunscreen use.

Reviews of the evidence generally refer to one notable randomised control trial (the gold standard type of study for health interventions) that showed a significant reduction in melanoma cases after ten years in participants assigned to use sunscreen daily.

A 2020 review from the Canadian Medical Association Journal detailed the current overall evidence base showing that use of sunscreen reduces skin cancer and pre-cancerous growths. Other large studies also back up the benefit.

Professor David Gawkrodger, British Skin Foundation spokesperson, told Full Fact, “With regard to the allegation that sunscreens cause skin cancer, [the post authors] give no reference for this and I have not seen any publication that says this.” 

We were also unable to find any such studies.

Systemic absorption and endocrine disruption

As the post notes, an FDA study found absorption of some substances in sunscreens from the skin to the bloodstream to be higher than previously thought. The researchers note this is an area requiring further research. But any actual impact on health from this is uncertain. The FDA states: “the fact that an ingredient is absorbed through the skin and into the body does not mean that the ingredient is unsafe, nor does the FDA seeking further information indicate such”.

The post claims “9 of the 15 chemicals found in most commercial sunscreens are known endocrine disruptors” that “interfere with the normal function of endocrine glands, leading to hormonal imbalances”. The post doesn’t list all nine chemicals it is referring to, although it does name three which it specifically says disrupt hormones further up. 

Oxybenzone

For example, it says oxybenzone, or benzophenone-3 as it’s known outside of North America, “is considered the most toxic of all sunscreen chemicals” and that it has been linked to hormone disruption among other things.

Studies in which rats were fed the chemical found hormone disrupting effects, but researchers found that it would take 277 years of daily applications of sunscreen to the face, neck, hands, and arms to reach the same amount of exposure as was given to these rats.

The European Commission Scientific Committee on Consumer Safety (SCCS) reduced the allowed benzophenone-3 levels in sunscreens for the whole body, from 6% to 2.2% due to these concerns, but “regarded the currently available evidence for endocrine disrupting properties of BP-3 as inconclusive, and at best equivocal.”

And the American Academy of Pediatrics (AAP) does advise “If possible, avoid the sunscreen ingredient oxybenzone because of concerns about mild hormonal properties” but adds “it's important to take steps to prevent sunburn, so using any sunscreen is better than not using sunscreen at all.”

But there is no conclusive evidence that use of sunscreens containing oxybenzone is harmful for humans. 

Dr Sophie J. Balk of the AAP’s Council on Environmental Health told Consumer Reports in 2019 “There's no research to prove adverse effects of oxybenzone on children, but there is concern.”

Other ‘hormone disruptors’

The post claims that homosalate (a UV blocking chemical found in sunscreens) disrupts hormones and “increase[s] the production of oestrogen in the body”. 

The SCCS found in 2021 that “The available data on homosalate provide some indications for potential endocrine effects. However, the current level of evidence is not sufficient to conclusively regard it as an endocrine disrupting substance”. 

Some lab studies using cells in isolation (‘in vitro’) have found oestrogen-like activity, but there have been no human studies to show this, and the majority of animal studies show no effect at all. 

Another UV blocker octinoxate is also claimed to be a hormone disruptor and “linked to reducing thyroid hormones in the blood”. The SCCS put out a call for data on the substance in 2021, but the results of this do not appear to have been published. 

The Commission’s previous review, from 2001, concluded “Based on the actual scientific knowledge, the SCCNFP [a precursor to the SCCS] is of the opinion that the organic UV-filters used in cosmetic sunscreen products, allowed in the EU market today, have no estrogenic effects that could potentially affect human health.” An Australian regulatory review from the same year concluded no action needed to be taken. 

We were unable to find any evidence of the chemical reducing thyroid function in humans. 

So while bodies like the FDA have recommended further research in this area it is misleading to claim (as the post does) that these chemicals are “known endocrine disruptors” in the context of normal sunscreen use. 

The information included in this article contains the latest evidence and official guidance available at the time it was written. This is not a substitute for medical advice. If you require specific medical advice please consult your GP.

Featured image courtesy of Moose Photos