8 Skincare Ingredient Combinations That Dont Mix Well

Layering skincare products can be tricky. Mixing certain products may make each of the active ingredients more effective, but the wrong pairings can lead to adverse effects (like irritation and skin 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."

So what skincare ingredient pairings should you stay away from? We spoke with Dr. Green and Dr. Craig Kraffert for all of the information on the combinations to be avoided at all costs.

BHA + Benzoyl 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 may risk irritating your skin. Keep the two separate to try to prevent redness and peeling. Its already a hotly debated topic whether benzoyl peroxide is safe to use on its own; adding a harsher product on top of it isnt going to be good for you. Dr. Green adds, "These ingredients all cause cell turnover and some degree of exfoliation. When combined, it would cause severe skin irritation."

Benzoyl Peroxide + Hydroquinone

If treating skin discoloration or pigmentation is your primary goal, mixing benzoyl peroxide and hydroquinone wont deliver results faster. Both ingredients can help fade leftover dark spots from acne, but using the two together can actually thwart the desired effects as the combination may stain the skin.

Benzoyl Peroxide + Retinoids

Simply put: These two acne-fighters dont play well together (and there is no loophole for using your tretinoin prescription to turn back the clock on fine lines and wrinkles either). Instead of amplifying the benefits, mixing the two will only degrade the potency of the retinoids.

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. The combination also might irritate your skin—particularly if youre sensitive to Vitamin C.

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 retinol 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[s] 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 may be somewhat unstable. So, you could (or if youre at all sensitive to retinol, you will) end up with aggravated skin that’s not even reaping the benefits of your products.

Retinol + Retinol

Perhaps this goes without saying, but well say it anyway: Dont layer multiple retinols. It probably wont end well. To avoid inflaming your skin, use only one at a time. Youll 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 thats 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.

Oil-Based + Water-Based Products

"Your products should have the same consistency," Dr Green explains. This means that oil- and water-based products—items with different consistencies—shouldnt be on your face simultaneously. Thankfully, it wont be dangerous 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."