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Layering skincare products can make each of the active ingredients you use more effective. However, certain skincare ingredients should never be combined—and when two ingredients clash, your skin ends up paying the price. Mixing the wrong products can lead to multiple days' worth of irritation, or it could even go so far as to cause burns. “You should err on the side of caution when combining certain skincare ingredients, and there are certain skincare ingredients you should never combine depending on your skin type,” Cosmetic dermatologist Michele Green, M.D., explains. “When in doubt it is best to use certain skincare ingredients separately or alternate each ingredient every other night or day.”
To make sure you’re never caught up in the aftermath of product layering gone wrong, we spoke with Dr. Green, as well as Dr. Craig Kraffert, a board-certified dermatologist, president of Amarté, and founder of Dermstore. They gave us all of the information on the combinations to be avoided at all costs.
BHA + Benzyol Peroxide
“Decreased tolerability is a concern whenever exfoliants (physical or chemical) are combined,” Dr. Kraffert says. Because beta hydroxy acids, like salicylic acid, and benzoyl peroxide are both exfoliating ingredients, you run the risk of irritating your skin. Keep the two separate to prevent redness and peeling. It's already a hotly debated topic whether benzoyl peroxide is safe to use on its own; adding a harsher product on top of it isn't going to be good for you. Dr. Green adds, “These ingredients all cause cell turnover and some degree of exfoliation combined together would cause severe skin irritation.”
Vitamin C + AHA
When layering vitamin C, you have to look out for active ingredient neutralization because antioxidants, like vitamin C, are inherently unstable. “Vitamin C is very pH sensitive, and mixing it with AHAs tends to substantially diminish its delivery within the skin,” Dr. Kraffert says. Powerful alpha hydroxy acids actually alter the pH level of vitamin C, which degrades its antioxidant properties. The combination also might irritate your skin—particularly if you're sensitive to Vitamin C, which many people are. As Dr. Green says: “These ingredients all cause cell turnover and some degree of exfoliation combined together would cause severe skin irritation.”
Vitamin C + Retinol
“Retinols and vitamin C should not be used together,” Dr. Green says. “When used together they can cause skin irritation.” She recommends using vitamin C in the morning, and then your retinols at night—with cleansing between, of course. “Retinol can make you photosensitive and Vitamin C works well when combined with sunscreen to combat free radical and photosensitivity.”
BHA or AHA + Retinol
Dr. Kraffert says there are a number of issues at play when combining AHAs or BHAs and retinoids. First, there’s the significantly increased potential for irritation that comes with combining exfoliating acids (like glycolic, lactic, and salicylic) with retinoids. And then, there’s also the matter of ingredient deactivation. Like vitamin C, retinol can be somewhat unstable. Alpha hydroxy acid oxidizes it, making it less effective. So, you could (or if you're at all sensitive to retinol, you will) end up with aggravated skin that’s not even reaping the benefits of your products.
Oil-based + Water-based Products
“Your products should have the same consistency,” Dr Green explains. This means that oil-based products and water-based products—items with much different consistencies—shouldn’t be on your face at the same time. Thankfully, it’s not going to be dangerous for you if you do, but it will be a waste. “[Not combining these products will] ensure proper absorption. The molecules of oil are bigger than that of water and therefore do not mix easily if at all,” Dr. Green says. “You should not use oil-based and water-based products as neither will absorb leaving a sticky residue on your skin.”
Retinol + Retinol
Perhaps this goes without saying, but we'll say it anyway: Don’t layer multiple retinols. It probably won't end well. To avoid inflaming your skin, use only one at a time. You’ll do more harm than good if you apply a retinol serum and top it off with retinol cream. You also might end up with a face that's itchy for days. “This includes taking care not to use your facial retinoids on the delicate eye area, followed by your retinol eye cream,” Dr. Kraffert says. The eye area is an easy spot to overdo it — be mindful of the active ingredients in your eye creams.