Your Sun Questions Answered: Expert Sun Tips From Chem PhD Lab Muffin

Science educator and chemistry PhD Michelle Wong, the beauty and brains behind the influential beauty blog Lab Muffin, gives us her expert sun tips on all things sun protection, including the most important of all: Just how do you reapply when you’re wearing all that makeup?

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Sunscreen application is a must, but did you know re-application is just as important? What about facial oils? Organic vs. Inorganic? (Or as many of us know it, chemical vs. mineral?)

Just because summer is drawing to a close, doesn’t mean we can be lazy about keeping ourselves safe. UVA and UVB rays are out there, 365 days a year. Maybe you’re finally starting to realize the importance of daily sun protection, or maybe you’re already on the straight and narrow but have some advanced questions. Wherever you fall on the knowledge scale, I’m here with some important expert sun tips, straight from a scientist!

I reached out to Michelle Wong, PhD, a “science educator” with a doctorate in chemistry and the delightful brains behind the Lab Muffin beauty blog to get an expert’s take on some of the pressing questions you might have about the finer points of sun protection. So let’s get started.

I just applied my sunscreen. Is it a good idea to immediately apply my BB cream?

 Michelle: For BB cream, I’d recommend letting the sunscreen dry for around 15 minutes, then applying BB on top. 

I wear a facial oil; will that interfere with my sun protection’s effectiveness?

 Michelle: There isn’t much research on this, but so far it looks like having an oil underneath can affect water resistance, and since water resistance is linked to the substantivity of the film (i.e. how well it stays as a uniform film), it’ll probably mean you’ll need to reapply sooner.

For products on top (e.g. BB, foundation), it looks like you should wait for the sunscreen film to set for about 15 minutes to limit how much it’s disturbed. It seems like pretty much anything disturbs it, but waiting 15 minutes in between things tends to help.

When should I reapply?

 Michelle: A second application around 15 minutes after sun exposure is good to make sure you don’t miss any spots and compensate for not applying enough in the first place (like a top-up). You should reapply every two hours, and if you’ve been in the water, if you’ve rubbed off any (by toweling off or with sand), or if you’ve been sweating a lot. In an office environment, there will be less disturbance to your sunscreen, but it’s likely that the film won’t be as even by the end of the day, so reapply before any sun exposure (or protect yourself from the sun in other ways with a hat or sunglasses).

How should I reapply?

 Michelle: Pretty much the same as applying in the first place — generously (1/4 tsp for the face), evenly, and without too much rubbing.

I started off with an organic sunscreen. Can I reapply with inorganic?

 Michelle: Zinc oxide and titanium dioxide (often called physical, mineral, or inorganic sunscreens) can interact and break down some organic (or “chemical”) sunscreens like avobenzone if it’s uncoated (and sometimes even when it’s coated). Unfortunately, it’s hard to tell whether it’s coated or not from the ingredients list alone. It’s safest to reapply the same sunscreen on top or sunscreens with similar ingredients.

OK, I’ve waited 15 minutes, and now I’ve beat my face for the gods, but I need to reapply my sun protection. How can I do this without messing up my makeup?

 Michelle: For reapplying, I’d recommend using a powder or spray sunscreen — and accepting that you’ll have less protection (and compensating by using a hat and sunglasses) — or reapplying using a cushion sponge.

Alternatively, if I’m going into the sun properly later that day, I don’t put on too much blush, etc., in the morning and just smoosh the sunscreen all over my face during reapplication. Then I redo powder and blush on top of that, and I usually look presentable.

Wanna learn more? Be sure to check out Michelle on IG @labmuffinbeautyscience (I love her skincare tips and beauty vocab posts!).

Do you have any expert sun tips you’ve learned? Please share the wealth so we can all avoid premature aging!