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Sunscreen filters: separating the wheat from the chaff (Part 2)

Natasha Dauncey blog post sun protection sunscreen

If you missed last week’s post on the importance of UVA and UVB protection you can read it here. Otherwise read on to learn more about the different options for UV filters.

One of the main reasons why people struggle to commit to daily sunscreen is that many formulations just aren’t “cosmetically elegant” (read: they feel bloody awful on the skin) or they can cause irritation / breakouts for some. For sunscreen to be worn daily, it’s obviously important that it feels nice on the skin and doesn't cause any negative effects. After all, the best sunscreen is one you can wear every day – and wearing something is always going to be better than nothing at all. It’s really important to remember this as it’s very easy to get carried away looking into the minutiae of sunscreen (yep, that’s me!). If you don’t have any skincare issues, your skin is not sensitive, or you're not overly concerned about UVA protection / anti-ageing, you can pretty much choose any broad spectrum sunscreen that feels nice on your skin.

My skin is fussier than that though, and I'm particularly interested in UVA protection, so I’ve had to do more research. Whilst I’m very happy with my current sunscreen, I’m still searching for a good (lighter) option for hotter months. Having tried quite a few now and after spending A LOT of time researching filters I thought I could share some useful info and links to other good sources. Skinacea has a great post that very helpfully lists nearly all the current filters as well as info on their alternative (INCI) names found on ingredients lists (deciphering these is half the battle if you don’t know the chemical names!).

Organic vs inorganic filters

You will often hear filters being described as physical (also seen as mineral) or chemical filters, though chemists don’t agree with categorising them in this way. Inorganic (physical) and organic (chemical) filters is felt to be a more accurate description as it reflects the chemistry of both types of filters. You may often see references to physical filters “blocking/reflecting” rays and chemical filters “absorbing” rays. In reality with a better understanding of how all filters work, both of these filter types absorb rays to a degree. I’m not going to pretend to be a chemist so if you want to understand the science behind sunscreen filters and see some common myths busted, check out Labmuffin’s and or Kind of Stephen’s blogs for more detailed information on the sunscreen and how it works.

Sunscreens can be formulated with either organic or inorganic filters, or a combination of both. Which you choose depends on what you’re looking for from a sunscreen and where in the world you live (i.e. which sunscreens you have access to).

Organic (chemical) filters

One of the reasons some people have been reluctant to use organic / chemical filters is that many of the older ones are associated with irritation and allergies. Also, many aren’t photostable (i.e. they break down in sunlight, defeating the purpose of using them!) and so need to be stabilised either by encapsulating them or adding in other filters/ingredients: avobenzone is a particular problem in this respect despite its good UVA protection. The main irritant culprits are avobenzone, octocrylene, ozybenzone and the less commonly seen PABA and padimate O (in the EU at least).

There are also concerns about some of the old filters being hormone disruptors, particularly oxybenzone, but also homosalate, octinoxate and padimate O to a lesser extent. Data inferring these claims is largely in vitro and in animal studies rather than in human studies and like with most things, it seems to be dose dependent and based on exposure levels much higher than what you'd get from a sunscreen. Given there are superior alternatives available where I live, I personally prefer to avoid the older filters (mostly due to the potential for irritation and the worry about photostability).

The newer filters available have been total game changers in my quest to find a daily sunscreen that I can get along with. They are associated with less irritation, better stability, have excellent UVA protection and are very wearable (less potential for white cast and lighter, more elegant textures). Unfortunately, they’re not available in the US, hence the strong focus on inorganic sunscreens there. We’re much more fortunate in Europe and other regions that these “newer” filters have been in use for several years. However, it’s still quite hard to find a well formulated sunscreen with exclusively new filters and even harder if you want to avoid fragrance (believe me, I’ve been trying!). A dedicated Reddit user has clearly spent a lot of time researching options for us though so his post is definitely worth a read as it was my starting point for finding my ideal sunscreen with new filters; my current favourite sunscreen came from his list. Having spent hours / days looking up sunscreen options I honestly believe this is the best list I’ve come across to work from for anyone searching for a fragrance free sunscreen that offers good protection. It’s very comprehensive and outlines not only filters, but also texture (important for different skin types), wear and likelihood of white cast (a dealbreaker for me!). For those of you outside the EU who may struggle to get hold of some of the sunscreens with newer filters that he lists, there are some inorganic options listed too.  

Key organic filters to look out for

Personally, I seek out for sunscreens with the following filters that all give good UVA protection:  Tinosorb S, M (which both protect against UVA1, UVA2 and UVB), Tinosorb A2B (UVA2, UVB) and Uvinul A Plus (UVA1, UVA2). As different filters have different “peaks” – the wavelengths at which they’re most effective, it’s good to have at least a couple of filters in a formulation. For UVB I also look for: Uvimul T150, Uvasorb HEB (also covers UVA1). There are also the Mexoryl SX and XL filters which are found in La Roche Posay and Vichy suncare (as L’Oreal holds the patent for these filters). I don’t actively seek these ones out though as they’re typically used along with the older filters (with a couple of exceptions). If you have sensitive skin and have previously ruled out organic filters, the newer ones are definitely worth trying (in a decent formulation for sensitive skin of course - check out that list!).

Inorganic (physical) filters

The two inorganic filters, zinc oxide (covering UVA1, UVA2 and UVB rays) and titanium dioxide (only covers UVA2/UVB) have often been considered a good option for sensitive skin especially in the past and seem to be favoured by dermatologists. It's also worth mentioning that zinc oxide offers some protection against visible light (HEV). HEV protection is starting to receive more interest, however there is limited study data around this topic currently. This hasn't stopped a few brands formulating sunscreens which claim to protect against HEV - though I'm not aware of any data to support these claims as yet.

Going back to UV protection, there are more filter options now (outside the US) many of which are felt to offer superior UVA protection by sunscreen experts and cosmetic chemists. I think it’s quite telling that in Europe inorganic-only sunscreens are more difficult to come by, as European brands seem more focussed on organic filters. The main issue with inorganic sunscreens is that a lot of formulations aren’t very wearable compared to sunscreens formulated with organic filters. They can feel heavy on the skin and tend to leave a very strong white / grey cast (both filters do this) which makes them near on impossible to use if you have darker skin like me and you’re applying the recommended amount. I don’t wear foundation most days so covering up the white cast with make-up is not an option for me. Reapplication would probably be a non-starter!

In order to tackle this issue, some inorganic sunscreens are tinted with so-called “universal tints” to mask the white cast but even so, very few are good colour matches for people of colour (or indeed for very fair skin tones). I’d love to see more shade options in tints to make them more user friendly. The other way brands have tried to minimise the white cast is to use micronised versions of zinc and titanium which reduces the particle size. The particle size can be reduced down so much that it becomes nano sized i.e. less than 100nm, and the labelling surrounding use of these nano particle sizes is very unclear and varies considerably by country. Whilst they're currently deemed safe for topical application there are still a lot of unknowns about they way they behave, the long term stability of the coatings used for nano (or non nano) zinc

Other as other aspects of a sunscreen formulation (e.g. distribution of filters, % of filters used, coatings used, other ingredients used) can affect the level of UVA protection a sunscreen affords. Look at the chart in Figure 3 on this other post from Kind of Stephen. This data was presented by J&J at an American Dermatology meeting last year and he assumed it related to Neutrogena Sheer Zinc SPF50. It shows the difference in level of UVA protection between 2 zinc oxide based sunscreens (among others), both of which have an SPF50. The chart shows that the Neutrogena sunscreen has a UVAPF of 30 (incidentally it has a very heavy white cast!), where as the Cerave SPF50 has a UVAPF of less than 15. 

Sunscreen formulation is incredibly complex - this is why you should absolutely stay away from DIY sunscreen formulations, using "natural" products which claim sun protection without appropriate labelling and testing, as well as mixing sunscreens with other products (foundations / pigments for adjusting tint or adding other sunscreens). There is no way to know how the formulation will behave. Go with a reputable brand, ideally one that indicates the level of UVA protection in its labelling, as you can see it can vary widely even in high SPF formulations. In the US, inorganic sunscreens or combination sunscreens containing zinc oxide are probably your best option but do make sure you look for a well formulated product from a reputable brand to ensure you’re getting enough UVA protection, since UVA standards of US sunscreens appear to be lower than in Europe.

Be aware that zinc is naturally drying as an ingredient and so those with oilier skins can sometimes get on better with an inorganic sunscreen than those with dry skin, unless the sunscreen has a lot of added hydrating ingredients to combat this. It’s also worth noting that zinc can calm and soothe the skin so if your skin is highly irritated, a sunscreen containing zinc might be a good option for you. Everyone responds to products differently though so your best bet is to try them for yourself!

A final point on inorganic sunscreens is that they can be quite difficult to remove from the skin. This is one of the reasons I favour an (emulsifying) cleansing oil to break down the any sunscreen without stripping the skin.

So that covers the choice of filters available to you and hopefully you now understand the differences between organic and inorganic options, as well as the differences within the organic category. It's certainly not clear cut and I think choosing a sunscreen is perhaps one of the most challenging aspects of nailing a good skincare routine! There are a few other things worth keeping in mind when choosing a sunscreen. Look out for next week’s post which outlines what else to look out for (as if this wasn't enough!) ;) .

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