6 Skin-Care Ingredient Combinations That Don’t Mix

Skin products may work well for you on their own, but do they all work in combination? “Some ingredients don’t play nice with each other,” says Brooke Sikora, MD, a dermatologist with SkinCare Physicians in Chestnut Hill, Massachusetts. Ingredients that people should avoid layering in a regimen are those that are difficult to keep stable in a formula, increase the risk of irritation together, or block each other out when a person uses them together, she says.

With a little know-how you can streamline your routine to make sure all the components are working for you and getting you closer to your good-skin goals. Here are scenarios where extra caution is in order.

Vitamin A derivatives like retinol and retinoids — and alpha hydroxy acids (AHAs) like glycolic acid — are a dermatologist’s go-to for anti-aging. They speed skin cell turnover and increase collagen production for glowy, fine line–free skin. Using them together, however, does not have the same effect. Because they both exfoliate the outer layer of skin, “they possess potentially irritating side effects, especially in combination,” says Elizabeth Bahar Houshmand, MD, a double-board-certified dermatologist in Dallas.

When skin shows signs of irritation (think: red, stingy, flaking, and peeling), you’re less likely to stick to the regimen. You don’t have to choose one or the other. She advises patients to use these topicals on alternate days (AHA on Monday, retinoid on Tuesday, and so on).

Retinoids may support anti-aging, but they’re also a powerful acne treatment, as they exfoliate skin to prevent clogged pores. As such, you may be tempted to use both a retinoid and a benzoyl peroxide. However, using these at the same time might not have the intended effects.

The third don’t-layer combo is retinoids and vitamin C. “Vitamin C is a tough ingredient to formulate with because it’s most effective in an acidic pH environment. Retinol works in a higher (more alkaline) pH. If using them together, they won’t work optimally,” says Sikora.

The easy fix is to use both at the times they were intended. Sikora advises that people get the most benefit from applying retinol at night, it makes skin more photosensitive, increasing risk of sun damage during the day. Conversely, vitamin C works best in the daytime, as it’s an antioxidant that protects against the skin-damaging effects of pollution and UV rays, she says.

Sikora advises that each can dry out the skin in isolation, meaning that extra caution is necessary when using both. Combining them risks making the skin too dry, which can lead to irritation and worsen symptoms. “To compensate for being overly dry, skin will ramp up oil production, which can create a vicious cycle of dryness and acne,” says Sikora. The fix: Use salicylic in the morning and your retinoid at night.

Using multiple forms of the same skincare product offers little benefit, says Dr. Hooper. One example is using two benzoyl peroxide acne products. Another example is applying a glycolic acid mask and then finishing with a cream containing mandelic acid, as both are AHAs.

“My concern with doubling up on the same active is irritation,” she says. Increased irritation is a sign that the products have disrupted skin barrier, Hooper explains, which only boosts the likelihood of suffering side effects from active ingredients.

That said, there is an exception: If you do this without incident — as in, your skin does not get red and stingy after using two AHA-containing products — and you’re getting the results you’re looking for, then Hooper advises that it is probably safe to continue. For most people, though, this is likely to be too harsh.

Combining skin-care ingredients may sound like a great idea for getting the best skin benefits from your regimen, but doing so can lead to irritation, overdrying, or reduced effects. Retinoids don’t combine well with AHAs, benzoyl peroxide, salicylic acid, or vitamin C due to potential stability issues and skin sensitivities, and soap-based cleansers can also reduce vitamin C’s skin benefits.

Using two products that have the same effects on the skin is also likely to cause irritation but might be fine for some people. Applying skin-care products on alternate days or at different times may prevent them from interacting, but asking a dermatologist about the best way to incorporate a product into your routine is often the most effective route for picking specific products.