Chemical vs. Physical Sunscreens: The Science Behind Their Effects

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. Not sure why one would have a combination of both as typically you have camp "I love inorganic aka physical" or "I love organic aka chemical ones". 

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. I know - for years now, big beauty companies tried to make you believe the one is better than the other and here we are now. As the sunscreen market is worth 14.9bn in 2024. So no, a physical isn't a shield you place on your face and every sun ray bounces of on you. This is one of the BIGGEST myth that one big company has ever created to sore their sales and generate fear among customers. 

The big differences between them that you should consider are:

PROTECTION LEVEL

A high SPF is pretty common with both types of sunscreen, although I would like to caveat this as mineral sunscreen are typically in your SPF 30 while there are more chemical or a combination of the two that actually are in the SPF 50 range. And the simple explanation is that you need approx 25% of zinc oxide to achieve a SPF 50. You can image what that might look like on your face and what it feels like. But broad spectrum protection (that includes protection against longer wavelengths of UVA) is where there’s a difference. And something that is not very common. 

Organic (what most people call chemical or even synthetic) sunscreens give higher, photostable protection from UVA if you use newer filters. And a fun fact; a lot of the newer filters are not available in countries like the USA. They still live in the dark-age using very out-dated sunscreens such as avobenzone . There are 27 UV-Filters available for chemists in Europe and a meagrely 16 UV Filters in the US that have been approved by the FDA. Avobenzone is the most common filter as it gives really high UVA protection, but it breaks down in UV. So if you see this ingredient, stay clearly away from it - unless you are a very diligent person in reapplying the sunscreen every other hour. And let's be true to ourselves - who enjoys reapplying their sunscreen? It is shocking to see how many brands still formulate in the 2024 with this outdated UV-Filter. 

Ultraviolet A Protection Factor, also known as UVAPF is a measurement of UVA protection. You can’t really tell what the UVAPF of a sunscreen is without actually testing it. And that's where it becomes interesting as not all R&D centers and all countries are equal and there is a HUGE difference in this. As it is also very expensive to test your sunscreen for UVA protection. Very roughly speaking, for sunscreens with a tested, publicly available UVAPF value, inorganic sunscreens get around UVAPF 20 max, if correctly formulated. While all the highest UVAPF sunscreens are organic can get around UVAPF 40% – if you’ve seen higher, let me know!. Our Everyday Sun Cream 50+ has reached an UVAPF of 40%. 

WHITE CAST

Organic sunscreens tend to leave less white cast while inorganic sunscreens tend to be very white (especially if they have titanium dioxide).

I am quite a fair skin person, 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 approx. 1/2 of a 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. And with zinc oxide and titanium dioxide there is always a white cast. I appreciate many brands are saying "You need to rub it in" but actually by doing so you rub off the sun protection again. 

TEXTURE

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. And you want to enjoy the feel of it otherwise you won't wear it. If you feel it is making you a little shiny. Then wait till it has settled and apply a light BB cream on top or a powder to remove the shine. 

SENSITIVE SKIN

If you’re in the US, avobenzone is in almost all broad spectrum organic sunscreens. Avobenzone is a common irritant and allergen, so it tends to be unsuitable for sensitive skin, and you’re left with inorganic sunscreens only as an option. But like I said as well, avobenzone is so outdated which is shocking that this is still found in modern and high-quality products. And brands who use it say "they are pioneering and innovative". Well, no. 

If you’re elsewhere in the world, the newer UVA1 filters aren’t irritating or allergenic. But you still need to be picky and looking for high-quality where still a lot of brands cut corners, as customers have a price point where they don't want to spend much. In Germany, most people don't want to spend more than 15 Euros or even less on a sunscreen. Considering a high-quality sunscreen can protect your skin from premature ageing, hyperpigmentation and skin cancer, my German fellow people are way too stingy. But hey, clearly have the money to invest into expensive laser treatments. 

A few other organic sunscreens also tend to cause allergic and irritant reactions: octocrylene, oxybenzone, avobenzone, PABA, Padimate O and enzacamene.

I only saw this combination again in a recent launch. I did had to check my calendar to make sure we are in 2024 and not back in the 60s. 

And non of these outdated and low-quality filters you find in our high-quality sunscreen. 

MYTHS ABOUT CHEMICAL AND PHYSICAL SUNSCREEN DIFFERENCES

There are a whole bunch of myths surrounding the topic of chemical and physical sunscreen. And here we have create a snapshot of some of those myths. Some of the most common myths are:

• 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. And that is the issue when brands who offer physical / mineral sunscreen say "you need to work it in / rub it in and the white cast goes away" - as this breaks and disturbs the continuous film on your skin as you are rubbing it on again. 

PHYSICAL SUNSCREENS ARE BETTER BECAUSE THEY ARE NATURAL

Natural things aren’t better than synthetic, man-made things.

Even if they were – physical sunscreens aren’t even natural. I said it before and I say it again. One cannot say phycial sunscreens are 100% natural. They simply aren't. 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. So can we please stop spreading this false statement? 

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 ARE EXPOSED TO SUN, BUT NOT PHYSICAL SUNSCREENS

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. 

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, especially if you’re active. And we simple sweat when it is warm outside and wearing a hat or glasses. If there is anyone that doesn't sweat under the glasses on their cheeks and nose - please email me! 

However, studies on daily sunscreen use found significant benefits even with once a day application and with regular activity.

YOU CAN USE LESS OF PHYSICAL SUNSCREEN

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% less by volume.

CHEMICAL SUNSCREENS ARE HORMONAL DISRUPTORS 

This is a complex topic.

There are a LOT of different chemical (organic) 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. At NAYA, we would still not use oxybenzone for many other reasons. But if you don't care and yo uare using oxybenzone, let me know how you get on in 200 years :) 

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. However, there is an ongoing debate when it comes to titanium dioxide and hence for NAYA this ingredient is an absolute no, no. In Europe, it is banned in foods and till the research data is clearer, we won't consider this ingredient. In addition, titanium dioxide is causing even more of a white cast on your skin. 

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. However, that is why we are using also antioxidants in our sunscreen that we have developed to protect the skin in addition and other ways. If your sunscreen doesn't offer any antioxidants than steer away from it unless you have a price point which isn't moveable. As antioxidants don't come cheap. 

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.

BOTTOM LINE

So at the end of all that: use whatever sunscreen works best with your skin need and skin concern (fading hyperpigmentation, sensitivity, allergies, acne). Ideally, it should have high UVB and UVA protection.

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: