Are chemical or physical sunscreens better? I touched on this in my Sunscreen and Make-up video, but a lot of people have been asking me to talk more about it, so I’ve expanded on the topic in this post, which comes in video form as well!
Click here for the video – scroll down for the blog post “summary” version with references and product recommendations (which is still somehow 1500+ words long…).
What Are Chemical and Physical Sunscreens?
The active ingredients in sunscreens are often divided into two categories:
- Physical sunscreen ingredients (more correctly known as inorganic sunscreen ingredients) are zinc oxide and titanium dioxide.
- Chemical sunscreen ingredients (more correctly known as organic sunscreen ingredients) are everything else.
You can have sunscreens containing only organic filters, only inorganic filters, or a combination of both.
The reason organic (carbon-based) and inorganic (not carbon-based) is a better classification than chemical/physical is that there’s overlap between how they work. Both types work by absorbing UV and turning it into heat. Inorganic sunscreens also scatter and reflect about 5-10% of the incoming UV, as do some particulate organic sunscreens like Tinosorb M, so really they should be classified as both chemical and physical.
Differences Between Chemical and Physical Sunscreens
The big differences between them that you should consider are:
SPF 50+ is pretty common with both types of sunscreen, but broad spectrum protection (that includes protection against longer wavelengths of UVA) is where there’s a difference.
Organic sunscreens give higher, photostable protection from UVA if you use newer filters like Tinosorbs S and M, and Uvinul A Plus (not yet available in the US). The more common avobenzone gives really high UVA protection, but it breaks down in UV so you have to be diligent about reapplication (although some formulas stabilise avobenzone so it breaks down slower, and you should diligently reapply sunscreen anyway if you’re spending a lot of time in the sun).
You can’t really tell what the UVAPF of a sunscreen is without actually testing it (sunscreen calculators like the BASF Sunscreen Simulator don’t accurately predict the protection of a finished formulation and should be used for formulating purposes only). Very roughly speaking, for sunscreens with a tested, publicly available UVAPF value, inorganic sunscreens get around UVAPF 20 max, while all the highest UVAPF sunscreens are organic (e.g. Bioderma and La Roche-Posay can get around UVAPF 40 – if you’ve seen higher, let me know!).
Organic sunscreens tend to leave less white cast while inorganic sunscreens tend to be very white (especially if they have titanium dioxide).
I recently got rematched with MAC shades and it turns out my skin has gotten paler thanks to my religious sunscreen use – I’m now closer to NC20 than NC25. But even though I’m on the paler end of the spectrum, inorganic sunscreens still commonly make me look mime-like if I apply 2 mg per square centimetre to get full protection, which translates to about ⅔ of a quarter teaspoon for me. This makes it hard to apply a generous amount, and since SPF scales with how much sunscreen you apply, this is an issue.
Related post: Video: How Much Sunscreen Do You Need For Your Face?
Sunscreens often have really thick, greasy textures and depending on your skin, one type might suit you better. I personally prefer organic sunscreens, since I’ve found quite a few that feel like moisturiser.
If you’re in the US, avobenzone is in almost all broad spectrum organic sunscreens (except for the ones containing L’Oreal’s patented Mexoryl SX). Avobenzone is a common irritant and allergen, so it tends to be unsuitable for sensitive skin, and you’re left with inorganic sunscreens only.
If you’re elsewhere in the world, the newer UVA1 filters aren’t particularly irritating or allergenic.
A few other organic sunscreens also tend to cause allergic and irritant reactions: octocrylene, oxybenzone, avobenzone, PABA, Padimate O and enzacamene.
Myths About Chemical and Physical Sunscreen Differences
There are a whole bunch of myths surrounding the topic of chemical and physical sunscreen. Kind of Stephen has written a great article on most of these myths where he goes into more detail about the studies.
You need to apply chemical sunscreens first and physical sunscreens last
You need to wait for chemical sunscreens to work but physical sunscreens work immediately
Both of these myths are based on the myth that chemical sunscreens need to absorb into your skin and bind before they work – but both types of sunscreen work straight out of the bottle.
All sunscreens just need to form a continuous film on your skin, and they’ll work, so you can apply them exactly the same way.
Physical sunscreens are better because they’re natural
Natural things aren’t better than synthetic, man-made things – I have a whole video on this topic: Video: Are Natural Beauty Products Better?
Even if they were – physical sunscreens aren’t even natural. They’re processed to get rid of toxic contaminants, and often need to be coated in synthetic chemicals to stop them from being photocatalytic, and prevent them from clumping up and causing patchy protection.
Chemical sunscreens produce heat which is bad for your skin
The amount of heat produced from UV by sunscreen is really, imperceptibly tiny. There’s also only a 5% difference in the heat produced by the two types of sunscreens, since physical sunscreens also absorb about 95% of the UV they protect you from.
You need to reapply chemical sunscreens if they’re exposed to sun, but not physical sunscreens (sort of true)
This myth is based on the idea that chemical sunscreens aren’t photostable, which means the molecules break down after absorbing too much UV and need to be replaced. But these days a lot of chemical sunscreens are photostable. The most photounstable combination is avobenzone and octinoxate, so it’s a good idea to reapply sunscreens with that combination frequently.
But you should really be reapplying ALL sunscreens, even without sun exposure. The main reason why you need to reapply sunscreen is that sunscreen shifts around and off your skin throughout the day, esepcially if you’re active.
However, studies on daily sunscreen use found significant benefits even with once a day application and with regular activity.
You can use less of a physical sunscreen (sort of true)
You need to use the same weight of chemical and physical sunscreen. But physical sunscreens tend to be denser, so on average you can use around 20% (⅕) less by volume.
Chemical sunscreens are hormonal disruptors (sort of true)
This is a complex topic.
There are a LOT of different chemical sunscreens. They have:
- different absorption rates – many new sunscreens don’t absorb into your body at all
- different UV efficiencies – so different amounts of each ingredient needs to be used to get the same UV protection, so our exposure to them differs
- different effects on the body – some have no known effects, some have hormonal effects
So you can’t make any blanket statements.
A lot of the fear is around finding these ingredients in breast milk and in urine. This sounds scary, but:
- detection methods are so sensitive now that teeny tiny amounts can detected, so finding something doesn’t mean there’s enough of it to have any effect
- the ingredient has to actually do something to be worth worrying about – for example, water is in breast milk and urine too
Out of the sunscreens, the one with the strongest hormonal effect is oxybenzone, according to in vitro studies on cells and animal studies (there haven’t been any human studies that have found a hormonal effect at the time of writing). One dermatology paper calculated that in humans, you’d need to use oxybenzone sunscreen continuously for 277 years to get the equivalent amount to cause a noticeable hormonal effect, so it’s considered safe.
Other sunscreens that have had hormonal effects in studies are enzacamene, padimate O, octinoxate and homosalate, although their effects are several orders of magnitude lower than oxybenzone, so the amounts you’d need would be even bigger.
Physical sunscreen nanoparticles are bad for you
Zinc oxide and titanium dioxide nanoparticles could potentially make reactions happen in your body, particularly in UV light. But the studies so far have found that the nanoparticles don’t get very far into the skin (only to the dead layers of the stratum corneum). It’s possible that nanoparticles will penetrate further if you apply them on broken skin, but they’re currently considered safe.
Sunscreens turn into free radicals
Both chemical and physical sunscreens have been found to react in UV light to produce highly reactive free radicals which can cause damage to surrounding substances, much like UVA. But these studies were generally performed in vitro with cell lines, while clinical studies on humans have found that sunscreens will reduce skin cancer and aging.
These reactions also only happen when enough UV hits the sunscreen, so they will generally only occur in the sunscreen film or in the upper, dead layers of your skin (same deal with retinyl palmitate).
So at the end of all that: use whatever sunscreen works best with your budget, skin type (oily, dry) and skin concerns (fading hyperpigmentation, sensitivity, allergies, acne). Ideally, it should have high protection (SPF 30+, broad spectrum).
I hope this answered a lot of people’s questions about the different sunscreen ingredients! If you want to learn more about sunscreens, there are a whole bunch more posts I have on them – here are a few:
- How Much Sunscreen Do You Need for Your Face? (Video)
- How to Get Vitamin D and Stay Sun-Safe (Video)
- Sunscreen FAQs (Video)
- What Does SPF Mean?
Some of these products were provided for editorial consideration, which did not affect my opinion. This post also contains affiliate links – if you decide to click through and support Lab Muffin financially (at no extra cost to you), thank you! For more information, see Disclosure Policy.