The hotter days are here and that means you’re probably getting bombarded with sunscreen content. Sadly, more often than not, you’ll see more scary misinformation, conflicting recommendations than actual helpful guidelines on just what to do to protect yourself from the sun. Fear not! We’re here to help tackle all of your sunscreen application questions with evidence-based suggestions. In this guide, we’ll cover the correct sunscreen application amount, just how should you layer foundation with sunscreen, and nerd out about the ins and outs of sunscreen-sunscreen layering.
How Much Sunscreen Should You Apply?
Okay - before we get into layering… we should revisit the correct application quantity. Studies have shown time and time again that most people are not applying nearly enough sunscreen to get the advertised level of protection. We don’t blame consumers at all! After all, it’s not intuitive to slather on huge handfuls of greasy, smelly goo. That said, skin cancer and long-term sun damage are no joke. So it is of the utmost importance to find a texture you’re willing to slather on generously.
If you want to start taking sun protection seriously, you’ll see many “guidelines” on just how much sunscreen you need to properly protect your skin. For your face & neck, you might have heard of the ¼ teaspoon, two finger, or even three fingers rule. Well - to put a stop to the rumor mill, the chemists tested this ourselves. You can review details of our test here but to summarize our findings:
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¼ Teaspoon is a very solid gauge no matter the sunscreen format
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If you don’t carry around a ¼ teaspoon in your purse, go for the 3 finger rule to be on the safe side. Using your fingers to guestimate the right amount of sunscreen is an okay method, but suffers from a lot of variability between different users.
Does layering sunscreen with makeup affect the degree of sun protection?
Okay, now that we have application quantity out of the way - let’s talk the age-old question “can you layer sunscreen with makeup?” The underlying million dollar question here is… “will layering these different products together affect the final sun protection level I’m getting?”
Luckily for us, we found a wonderful study that looked at just that:
Study Breakdown
The study aims to look at the SPF value you would get from layering products in a way that mimics “real life applications”. What this means ini this study is that instead of applying the standard 2 mg/cm2 worth of sunscreen, it purposely “under applies” the sunscreen the the products (sushion foundation, liquid foundation, and compact powder) thereafter. Each of the product comes with its own SPF value.
After each of each study scenario, the SPF value is measured at the end of application:
Key Sunscreen + Foundation Takeaways
Here are the important takeaways from this study:
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If each of he product you’re layering has SPF, it can help ensure that you’re getting some level of protection
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Under-application is definitely still an important factor to consider. More is more!
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This study is notably done on international filters not available in the US - it’s one case study and doesn’t guarantee sunscreen stability across all product types
Pilling: The Red Flag of Sunscreen + Makeup Layering
At the end of the day, sunscreens NEED to form a robust protective film for it to work well. To layer foundation on top, there are risks of ingredient or formula incompatibilities that compromise sunscreen performance.
So regardless of the types of makeup you’re layering with your sunscreen, the most definitive red flag for your particular product combination is “pilling”. Pilling is when your products form little balled up eraser dust like crumbles on your face. It is a telltale sign that your sunscreen is most likely not forming that even, robust film that it needs to form for proper protection.
We foudn a really insightful studies that looked at different product layering scenarios and the pilling potenials that they come with:
Study Breakdown
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528 participants (women, aged 20–49) given common products to layer as they would in real life scenarios
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Pilling events were then observed and recorded
Results Summary
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Sunscreen alone: 59 volunteers experienced pilling
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Sunscreen over skincare: 655 pilling events (12.4%)
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Foundation over skincare: 0.66% pilling
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Foundation over skincare and sunscreen: 1.16% pilling
Key Takeaways
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Drier skin, higher pH, and smoother texture = more pilling
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Some people only pilled with sunscreen alone, others only when layered. Group C had it the worst — pilling with everything.
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Weird but wonderful: In many cases, adding foundation reduced pilling. 🤯 But if your sunscreen pills on its own, stop there. Don’t pass go, don’t collect your setting spray.
Avobenzone: The Chaos Agent of Sunscreen + Sunscreen Layering
Another angle to consider when it comes to sunscreen layering is the presence of avobenzone. This sunscreen filter is the root of many many US-based chemist woes. As of now, this is the ONLY chemical filter available to get “broad spectrum” claims to ensure your sunscreen also offers UVA protection. Sadly… avobenzone is notoriously in credibly finicky and unstable… especially in the presence of mineral filters.
Now as chemists who’s dealt with many sleepless nights formulating with this ingredient, we can tell you that there are many ways to help stabilize your avobenzone. However, it’s still a sensitive ingredient you have to monitor with every tweak. This is why layering multiple sunscreens — especially if one contains avobenzone and the other is mineral-based — can create instability. Thre are different types of mineral formula that can work with avobenzone, but there’s simply no way for you to know for sure.
The simplest course of action here is to layer your avobenzone products with other products with avobenzone. This at least buys the insurance policy that all the products your’e using have factored in avobenzone instability, lowering the risk of sunscreen degradation.
Our Sunscreen Layering Philosophy
Phew! Okay, so that’s a lot of studies and information. So let’s summarize everything into practical guidelines:
Tier S: One-and-done sunscreen. To play it safe, your last layer should always be sunscreen you’re willing to apply liberally. This is the most surefire way of getting that advertized level of protection. But we get it — real life isn’t a clinical trial.
Tier A: sunscreens that uses international (EU/Asia) chemical filters or mineral filters layered with foundation. Bonus points if that foundation also comes with some level of SPF protection. This combination has less chance of surprise sunscreen filter degradation.
Tier Awkward: sunscreens with avobenzone. This finicky filter is the root of many chemists woes in the US. Layering this with minerals is generally awkard. There are ways to stabilize… but you’re just not so sure if your particular combination is okay. If you have a sunscreen love that features avobenzone, it’s best to layer with other products that also have avobenzone. The working assumption here is that both products have taken the time and effort into stabilizing avobenzone, so the combination should be okay.
Tier Nope: Anything that pills. No exceptions.
References
Lua, B. L., Ruan, L., Lyu, Y., & Liu, S. (2024). Understanding the causes of skincare product pilling. Skin Research and Technology, 30(8), e13828.
Kim, M. A., Jung, Y. C., Bae, J., Ha, J., & Kim, E. (2021). Layering sunscreen with facial makeup enhances its sun protection factor under real‐use conditions. Skin Research and Technology, 27(5), 751-757.
Dondi, D., Albini, A., & Serpone, N. (2006). Interactions between different solar UVB/UVA filters contained in commercial suncreams and consequent loss of UV protection. Photochemical & Photobiological Sciences, 5, 835-843.
Goral, O., Zukowska, G. Z., Zero, E., Siekierski, M., & Krzton-Maziopa, A. (2024). Understanding Avobenzone Crystallization in Sunscreen Formulations: Role of Metal Oxide-Driven Nucleation and Stabilization Strategies. Crystals, 14(7), 663.
Le Digabel, J., Questel, E., Lauze, C., Carballido, F., & Josse, G. (2023). In vivo evaluation of sunscreen application by multispectral imaging: A new tool for educating sunscreen users. Skin Research and Technology, 29(8), e13320.
