Can they be mixed? Yes, with reservations

Two of the hottest skin care ingredients of the moment might be a little too harsh to be used together, so Gohara actually recommends using them in different parts of your routine. "I like using vitamin C in the morning, right after I get out of the shower, and use a retinol at night," she says. Since "ultraviolet light can inactivate retinol" and "Vitamin C makes a good warrior against free radicals you come in contact with during the day," you get the best of both worlds that way. Gohara notes that this logic holds true for other antioxidants as well.

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Can they be mixed? Yes

Vitamin C is also known as ascorbic acid, which begs the question: Is it overdoing it to mix it with your favorite acid toner? Gohara gives you the go-ahead, though watch for overdrying.

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Can they be mixed? No

Though they're cornerstone ingredients in a lot of skin care routines, you might want to avoid mixing your retinols and AHAs. "Retinols and AHAs may be too irritating to layer on top of each other," cautions Gohara. Patel adds that strong concentrations can "cause increased skin peeling and even redness/irritation."

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Can they be mixed? Yes

You've probably noticed that antioxidants vitamin C, vitamin E and ferulic acid are often used together — and that's because the addition of ferulic acid actually helps stabilize the vitamins C and E while also boosting their efficacy. Throw just the right amount of retinol in there and you're really cooking with gas — though it's worth pointing out that Patel recommends searching for a product that combines them (like Visha Skincare Advanced Correcting Serum with Illuminotex) rather than trying to layer them together yourself.

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Can they be mixed? Yes

Though the name might sound harsh, hyaluronic acid is actually super gentle and hydrating, which makes it a great follow-up to some of your stronger skin care ingredients. Gohara says it works especially well with AHAs since the AHAs help pave the way for all the hydration you get from the hyaluronic acid. Similarly, a hydrating cleanser like the Dove White Beauty Bar is safe to mix with other ingredients, especially since it helps keep the skin barrier healthy.

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