“The biggest issue with mixing certain actives, or skin-care ingredients, is they can cause dryness, burning, stinging, or redness of the skin” and, sometimes, discoloration, says Caren Campbell, MD, a board-certified dermatologist in California. “Additionally, some skin-care active ingredients negate the effects or reduce the effectiveness of others.”
To prevent your skin-care routine from becoming a chemistry experiment gone wrong, keep scrolling to find out which ingredients derms are begging you not to mix.
1. Vitamin C and exfoliants
Shirley Chi, MD, a board-certified dermatologist in California, says to never use vitamin C after exfoliating. Exfoliating ingredients include alpha-hydroxy acids (AHA), like glycolic acid, beta-hydroxy acids (BHA), like salicylic acid, and scrubs. This rule applies to the serums you use at home as well as to any in-office exfoliating treatments, like chemical peels. “I always recommend that you do not use vitamin C serum right after you do anything like that,” says Dr. Chi, “It’s very irritating, and does more harm than good because your pores are so open.”
How to exfoliate your face:
2. Retinoids and hydroxy acids
Another ingredient you’ll want to keep away from your AHAs and BHAs? Retinol. Though retinoids are great for stimulating cellular turnover, they also have the potential to cause irritation—and that risk factor increases when you’re using them on freshly exfoliated skin. “Using AHAs and BHAs along with retinoids can cause excessive dryness,” says Dr. Campbell. To avoid irritation, she suggests using glycolic wash one to two times per week to exfoliate, and using a retinoid on your non-exfoliating nights.
3. Different types of retinoids
We love retinoids because they give you clearer, brighter skin—but you don’t want too much of a good thing. You’ll find retinoids most commonly listed as retinol, retinaldehyde, retinyl esters, tretinoin, adapalene, tazarotene, and trifarotene, and Dr. Chi says to avoid doubling up. “If you’re going to put on a serum that has retinol and then you put on adapalene, that’s probably going to cause irritation because now you’re amping up your adapalene,” says Dr. Chi. Pay attention to ingredient labels to ensure you’re not doubling down on the potent active.
Learn more about retinol here:
4. Certain retinoids and benzoyl peroxide
Benzoyl peroxide is a topical antiseptic that’s commonly used to treat acne, and retinoids are known to quash breakouts by replacing the dead skin cells on the surface of your complexion with healthy new ones. But when using them together, check with your dermatologist to ensure they’re compatible. “Certain retinoids can be deactivated by benzoyl peroxide, but not all,” says Dr. Campbell. She names adapalene as one of the best over-the-counter retinoids that you can use alongside benzoyl peroxide without any issues. If you do want to use both ingredients in tandem, Dr. Campbell recommends packing your nightly routine a benzoyl peroxide wash, like CeraVe Acne Foaming Cream Cleanser ($12) in the shower, followed by an adapalene serum, like Differin ($16), when you get out.
5. Copper peptides and vitamin C
Copper peptides are becoming popular in skin care due to their ability to stimulate skin renewal. Just make sure you don’t mix them with vitamin C. “Copper peptides should not be used with vitamin C as they can oxidize Vitamin C and reduce its antioxidant effect,” says Dr. Campbell. To achieve the maximum benefits of each ingredient, split them between your morning and evening routine or use them on alternating days.
Here’s why vitamin C is so good for your skin:
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