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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Can they be mixed? No

This might sound a little kooky, but Patel breaks it down: "Acids by nature have a low pH and if they are layered under products that are basic in pH, they will become less active." You know what's typically basic? The tap water you wash your face with every day. "Properly drying your face and rinsing off soap (which is also alkaline) will help your various skin care acids work better," she explains.

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