There’s been a few viral posts about how harmful chemical sunscreens are. The latest one is a post about “Sunscreen Swaps” from @a.glimpse.of.amelia (an Australian “low-tox” consultant) and @jordiepieface (a nutritionist from New Zealand), claiming that “some conventional sunscreens can do more harm than good”.
Unfortunately, most of the post is inaccurate, and it’s likely scaring people away from using sunscreens that work for their budget and preferences. Here’s the lowdown…
Sunscreen and skin cancer
First, some quick reminders:
- 2 in 3 Australians will be diagnosed with skin cancer by the age of 70.
- Too much UV causes up to 95% of melanomas and 99% of non-melanoma skin cancers in Australia. It’s one of the most preventable causes of cancer!
We all want to prevent health problems. But avoiding well-studied and regulated anti-cancer products because of misunderstood data won’t actually improve our health.
Harmful chemical ingredients?
The post starts by saying to “Avoid these harmful chemical ingredients“. This is only necessary if you’re allergic – sunscreen filters aren’t harmful at the levels used in sunscreen.
Sunscreens are some of the most scrutinised products we use! They’re therapeutic goods/drugs in Australia and the US, and special cosmetics in the EU, Korea, Japan, etc. This means safety assessors are looking at the same scientific studies that organisations like the EWG, Yuka, and the Campaign for Safe Cosmetics cite… except safety assessors are interpreting them in context.
Studies finding links to health effects and potential issues often use unrealistic quantities and exposure routes – for example, rats eating thousands of times more sunscreen than you’d ever use. This is to find ANY possible tiny health effects, to really make sure we’re using them safely. It’s like testing if a car is safe – it’s fine if you don’t see problems normally driving it, but it’s so much more informative if you test what happens during unusual situations, like super high speed crashes.
“These sunscreen ingredients are concerning due to their potentially harmful effects, especially for children and pregnant or breastfeeding women:”
You’ll notice a lot of vague words, like “potential”, “linked to”, “can”, “may”. These links are usually only observed under unrealistic conditions. Scientists generally like cautious conclusions. The actual uncertainty is much less than it sounds!
Sunscreen safety assessments cover everyone over 6 months old, including pregnant people. Regulatory limits are usually based on potential effects on foetuses (since they’re particularly sensitive) in pregnant animals.
Oxybenzone
“OXYBENZONE: A known endocrine disruptor, it can interfere with hormone function and has been linked to reduced sperm quality.”
“Endocrine disruptor” means something has the potential to interfere with your hormones. It doesn’t actually happen unless there’s enough.
The EU reassessed oxybenzone in 2021. They found:
- There wasn’t enough evidence for endocrine disruption
- It would still cause little to no harm at over 220% in sunscreen, even used all over your body daily.
They use a 100-fold margin of safety, so it’s allowed in EU sunscreens at 2.2% (100 times less than 220%). It’s in Australian sunscreens at up to 10%, which is still not predicted to be a problem.
The link to reduced sperm quality has only been observed when oxybenzone was added to sperm in a petri dish – not when oxybenzone-containing sunscreen is used on people.
Octinoxate
“OCTINOXATE (OCTYLMETHOXYCINNAMATE): Mimics estrogen and may disrupt thyroid function, potentially throwing your hormones out of balance.”
Again, “may” and “potentially” are doing a lot of heavy lifting.
Natural hormones are very potent – you would need very large amounts of sunscreen ingredients to interfere with them. Octinoxate only has very very weak oestrogenic activity (it’s a partial agonist).
The amounts used in sunscreen have not been documented to cause endocrine disruption, even though octinoxate has been used for decades.
Homosalate
“HOMOSALATE: Another endocrine disruptor that lingers in the body, adding to your toxic burden over time.”
Some weird claims here – homosalate doesn’t “linger” more than other ingredients, and “toxic burden” is very vague. This feels like it’s not based on anything concrete.
The EU did recently lower the homosalate limit to 0.5%, which sounds scary, but note:
- The 100-fold margin means they calculated that 50% homosalate sunscreen used daily, all over your body, should still cause little to no harm. This goes up to 734% for daily face use.
- This finding was in June 2021, but you can still buy 10% homosalate sunscreens in the EU until July 2025. That’s 4 years!
So it isn’t like 10% is concerning enough for warnings or recalls. This is just part of the process of making very safe products even safer.
They also found that there wasn’t enough evidence to say it’s an endocrine disruptor.
Octocrylene
“OCTOCRYLENE: Linked to skin allergies and produces free radicals when exposed to UV rays, which can damage cells and even cause mutations.”
More weird claims! Octocrylene is actually one of the most UV-stable sunscreen ingredients.
On the other hand, mineral titanium dioxide (which they recommend) is notorious for producing free radicals in UV! It should still be fine, since this happens in the top dead layers of skin – you’d need an awful lot to damage cells and cause mutations.
Allergies are when you react to something normally safe – not everyone needs to avoid them (e.g. I am allergic to cats).
Avobenzone
“AVOBENZONE (BUTYL METHOXYDIBENZOYLMETHANE): Breaks down into toxic compounds when exposed to sunlight and water, generating free radicals that accelerate ageing and may increase cancer risk.”
Avobenzone does break down easily in UV if the formula isn’t stable. Octocrylene is actually really good at stabilising avobenzone!
Modern formulas are usually very stable, giving high protection even after a full day of sun – you’ll sweat the sunscreen off before it breaks down significantly.
The Nambour trial in the 1990s found that an avobenzone sunscreen reduced skin cancer and ageing. Sunscreens are much better now!
4-Methylbenzylidene Camphor
“4-METHYLBENZLIDENEy CAMPHOR: Research suggests it may harm the thyroid and disrupt hormones, and European authorities recommend avoiding it altogether.”
4-MBC will actually be phased out in the EU in May 2026, but again, this is 4 years after the safety assessment. New products can still be launched until May 2025.
The reason isn’t because they found it was unsafe, but because there wasn’t enough data to work out what the new limit should be.
Again, this shows that sunscreens are very safe, and they’re constantly being made safer!
It’s an interesting choice to cite this EU recommendation but ignore the rest. This is an example of cherrypicking evidence, instead of presenting the full picture objectively.
Chemical vs mineral sunscreens?
Next there are some claims about the differences between chemical and mineral sunscreens, most of which are incorrect, and I’ve debunked before.
“Mineral-based sunscreen is generally considered better than chemical-based sunscreen, especially for those with sensitive skin, children, or those looking to avoid potential exposure to harmful chemicals.”
This isn’t true – we’ve gone through harmful chemicals already. Children over 6 months can use any sunscreen safely, unless allergic, and babies under 6 months shouldn’t use any sunscreen at all. Mineral sunscreens can be a better option for people with sensitive skin, but there’s a lot of nuance that we’ll get into a bit later.
The best sunscreen is the one you enjoy enough of to apply a lot of, regularly. For most people this is a chemical sunscreen – they’re more lightweight and can have no white cast, even on darker skin. But if you prefer mineral, that’s fine too! Just make sure you apply enough.
Key ingredients
“Chemical sunscreens: Synthetic filters like oxybenzone or octinoxate. Some of these chemicals are linked to hormone disruption, skin irritation, and environmental harm.”
“Mineral-based sunscreens: Natural physical blockers like zinc oxide and (non-nano) titanium dioxide.”
We covered most of this already! But chemical sunscreens also aren’t worse for the environment. Natural doesn’t mean safer – petroleum is natural, but oil spills are still bad! Arsenic and lead are also natural. (More on environmental impact later…)
Zinc oxide and titanium dioxide in sunscreens also aren’t very natural – they’re often synthesised, because natural sources aren’t very pure. Mining and purification also have large environmental impacts.
How it works
“Chemical sunscreens: Absorbs UV rays and converts them into heat.”
“Mineral-based sunscreens: Sits on the skin’s surface and reflects UV rays.”
Both mostly absorb UV and convert it to heat – only 5-10% of UV is reflected or scattered. Absorption is better anyway, since it actually gets rid of the UV!
Skin safety
“Chemical sunscreens: Can irritate sensitive skin or cause allergic reactions; may sting eyes.”
“Mineral-based sunscreens: Gentle on sensitive skin; unlikely to irritate or cause allergies.”
I actually agree with most of this one! However, newer chemical sunscreen filters are also great for sensitive skin and eyes, and some people (e.g. me) break out more with mineral sunscreens.
Mineral sunscreens also often contain SPF boosters which are harder to spot, which can be a big problem for people with chemical sunscreen allergies.
Application
“Chemical sunscreens: Requires 15-30 mins to become effective after application.”
“Mineral-based sunscreens: Works immediately after application.”
All sunscreen ingredients work immediately, but all sunscreens need a bit of time to dry down and form an even layer. You’ll see “apply 20 minutes before sun exposure” on mineral sunscreens too!
Systemic absorption
“Chemical sunscreens: Filters can enter the bloodstream; effects are still under study.”
“Mineral-based sunscreens: Remains on the skin’s surface, reducing systemic exposure.”
Technically this is true, but again, all sunscreens are very safe. The difference is much, much smaller than it sounds (see earlier slides for details on specific ingredients).
Environmental impact
“Chemical sunscreens: Linked to coral reef bleaching and aquatic toxicity.”
“Mineral-based sunscreens: Reef-safe when free of harmful nanoparticles and chemicals.”
Nope – the National Academies gathered a bunch of the top experts on aquatic toxicity to look at sunscreen’s impacts in 2022. They found that chemical and mineral impacts overlap.
For corals specifically, they found that most chemical sunscreens are less toxic than zinc oxide (not just nano zinc oxide). They also criticised the bans in some places as premature, and not based on reliable evidence.
This diagram from the National Academies report illustrates this really nicely – each black dot is the amount that caused a toxic effect in a study. The lower a dot is on this graph, the less you need of that ingredient to have the harmful effect.
Appeal to emotion is a red flag
I think the best advice for working out if a post like this is true or not is to use the SIFT method:
- Stop
- Investigate the source
- Find better coverage
- Trace claims, quotes, and media to their original context
The most important part of this is the first step: If a post makes you feel scared, STOP before you take any action, like sharing the post or throwing out your products. Strong emotions can stop us from thinking critically – we all care about our health, so making scary claims about common, well-known products is an easy way to catch attention.
Thanks to Mo Skin Lab (toxicologist and safety assessor) for looking over the Instagram post for me!
