Nothing takes off goop and grime like an oil cleanser. As board-certified dermatologist Dr. Christine Choi Kim explains, you just can't beat it. “The idea of ‘like dissolves like’ is really what the whole K-beauty double cleansing method is based on,” she says. “A lot of long-wearing products have an oil base, so you'd take off all your oil-soluble products with an oil-based cleanser.” Waterproof mascara, red lipstick, full-face foundation, and heavy sunscreens all melt away with just a little bit of oil.

[Record scratch] Yup, you read right. Oil's the best at removing sunscreen. But what about if you're wearing oils to moisturize and sunscreen to protect? At the end of the day, there's not much of a difference between cleansing oils and facial oils—the former just rinses off easier, and the latter tends to include more expensive ingredients. I had called Dr. Kim to get to the bottom of it.

You know that a sunscreen with SPF 30 protects better than with one with SPF 8, but an SPF value doesn’t tell you much about how a sunscreen performs against real world conditions. Reveals Dr. Kim, “Sunscreens are essentially assigned their SPF in a vacuum.” For example, sunscreens are actually tested on back skin, not notoriously sensitive and oily face skin. Plus, most people aren't using moisturizers and makeup on their backs. SPF isn't tested to account for that kind of stuff. “We simply do not know the effect that facial oils could have on the effectiveness of your sunscreen,” Dr. Kim confirms. (For more on how SPF testing works, check out this link.)

Basically, facial oils might break down your sunscreen. Or they might not! Because of the way sunscreens are tested, it's really a big question mark.

“If you want to be very conservative,” suggests Dr. Kim, “use your facial oil at a time of day you’re not also using sunscreen.” Not only will this ensure you’re getting the exact level of sun protection advertised on your sunscreen, it can also help boost the efficacy of both your sunscreen and your oil. In the morning, prioritize sunscreen over oils—oil might make you look glowy right now, but UV damage is the cause of [90-percent of visible aging] and SPF protects against that. Plus, as Dr. Kim explains, “Facial oils shine at night, because a lot of them have regenerative benefits.” You’re basically helping your skin work harder while you sleep. It’s great!

Another good solve? Finding a sunscreen that’s super moisturizing and leaves a glowy finish without extra help. “These are made with nourishing oils and tested as a complete formulation,” says Dr. Kim—in other words, the chemists dealt with finding a balance between oils and UV filters so you don’t have to worry about it. What you see is what you get. For days you’re mostly indoors, Dr. Kim particularly loves the Yes To mineral lotion, which features dry skin saviors like avocado and coconut oils, plus glycerin. (She recommends the affordable drugstore line so often she’s actually become a brand ambassador.) Other deeply moisturizing sunscreens include Kinship’s Self Reflect, Supergoop’s Zincscreen, Josh Rosebrook’s Nutrient Day Cream, and Black Girl Sunscreen.

Or, you can also just be strategic about your application. Instead of slapping on your sunscreen while your facial oil still feels slick, wait for it to sink in. (When your skin really needs it, oil won’t slip and slide over the surface for long.) If you’re still worried about your sunscreen degrading, just make sure you apply a good amount to start and reapply during the day. Dr. Kim reiterates that the American Academy of Dermatology recommends you use an ounce (that’s one full shot glass) of sunscreen to cover your face and body, and reapply every two hours when you’re outside. But at the very least, you should use enough sunscreen on your face to feel that something’s there. “When you’re using something like a retinoid, you want to just use a pea-sized amount—less is more. But sunscreen should feel like a layer on your skin,” she explains. “If you can’t tell it’s there, you probably need to use a little more.”

TLDR, because it’s hard to say for sure how any of your beauty routine affects your SPF, just try to be cautious. And maybe grab a brimmed hat on your way out.

—Ali Oshinsky

Photo via ITG