Acids, retinol, vitamin C—the skin-care world is filled with powerful ingredients that promise to deliver a supermodel-worthy complexion. In fact, there are so many products on the market containing these ingredients that it’s tempting to simply slap on as many potent formulas as possible and cross your fingers for that Gigi Hadid glow. But the reality is, not every skin-care ingredient is compatible with the next and mixing certain ones together can actually have detrimental effects on your skin.
“Often, products are very carefully and expertly formulated to achieve a combination that effectively solves a problem, treats a condition, or serves a skin need,” says Dr. Ava Shamban, a board-certified dermatologist in Los Angeles. “Adding or mixing something else could potentially destroy its efficacy and [the] activity of some of its key ingredients. Or worse, since not all ingredients play well together, they can clash and cause irritation, burning, or other dermal disasters.” In order to avoid an accidental, self-inflicted skin woe, we asked the experts for the ingredient combos that should never be used together. You’ve been warned.
AHAs and vitamin C
AHAs, aka alpha hydroxy acids, work as chemical exfoliants to improve texture, reduce fine lines and dark spots, and bring brightness to an otherwise dull complexion. While some people can tolerate using both vitamin C and an AHA (like glycolic acid or lactic acid) in their routine, there is a caveat. “Depending on the pH, acids can enhance the effectiveness of vitamin C because this ingredient is super pH-sensitive, and various forms of vitamin C are actually very unstable,” Dr. Shamban explains. “Too powerful an AHA will alter the pH of a vitamin C [product], which will both degrade its antioxidant power and irritate. If you use a product that does not affect the pH, [they] can work very well together and actually enhance [results].” So for those generally used to more advanced skin protocols, your skin can most likely tolerate acids with vitamin C. However, more sensitive or reactive skin cannot. “If in doubt, don’t double down,” advises Dr. Shamban.
Acids and benzoyl peroxide
If you’re using benzoyl peroxide for breakouts, be wary of using it with your acid products. “In general, the categories of beta hydroxy acids [BHA], alpha hydroxy acids, [or even polyhydroxy acids (PHA)] are pretty potent exfoliating ingredients,” Dr. Shamban says. “Mixing with other [drying products], such as benzoyl peroxide, may be too harsh and [cause] irritation, peeling, and inflammation or redness—even though each [product] is good on its own.” Since benzoyl peroxide can parch the skin, Dr. Shamban usually recommends using a product that is hydrating and moisture-binding on top of it so that your complexion doesn’t get too dry and act counterintuitively, resulting in an overproduction of sebum and more breakouts.
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Retinol and acids
Many skin-care fans swear by retinol products for everything from acne to wrinkles to improving texture, pigmentation, and scarring. However, retinol is a seriously strong ingredient, and you can’t throw it into your routine with all your other products—especially acids. “Retinols and acids, physical exfoliators, and AHAs/BHAs are generally best to avoid using together unless a product is formulated specifically with the two ingredients—for example, SkinBetter AlphaRet Overnight Cream [$125]—given there’s an increased risk of irritation associated with using the two together,” explains Dr. Marisa Garshick, a board-certified dermatologist in New York City. “This is because exfoliants remove a layer of dead skin, making the skin more vulnerable to irritation from the retinoid if used directly together.” Dr. Shamban also mentions the combination of retinol and acids as a “never-ever” because it can result in “irritation, redness, inflammation, and sometimes, a full-blown irritant dermatitis.” If you want to use both retinols and acids in your routine, just alternate the days, to avoid the risk of a reaction.
Chemical and physical exfoliators
The idea of doubling down on exfoliating might sound good if you’re experiencing rough or dull skin, but Dr. Garshick says it’s important to avoid using chemical and physical exfoliators at the same time. Chemical exfoliators work by dissolving the “glue” that connects dead skin cells, therefore aiding in cell turnover. Physical exfoliators, on the other hand, manually remove those dead skin cells through the use of a scrub or brush. While both can individually work wonders on dull skin, they can be too harsh when used together. “Although some people like the feeling of exfoliation from a scrub, it is important to not use a chemical exfoliator at the same, as this can contribute to overexfoliating, which can lead to dry, irritated skin,” she says.
Salicylic acid and benzoyl peroxide
If you’ve got a zit the size of Texas, you might be tempted to slather on every acne product known to man—but please don’t. “Although salicylic acid and benzoyl peroxide work for different components of acne breakouts, it is best not to use the two at the same time,” Dr. Garshick says. Why? “It can lead to excessive dryness—which can, in turn, tell the body to produce more oil, contributing to worsening breakouts.”
Skin-care devices and products
If you’ve ever thought there might be risks associated with using your favorite at-home skin-care device—like a Clarisonic—with your skin-care products, you were right. “Clarisonics offer some degree of exfoliation by eliminating a layer of dead skin, which, while it can help improve penetration of certain ingredients, can also make the skin more sensitive,” Dr. Garshick says. “If using a Clarisonic, I recommend only using it with gentle products to provide a deeper cleanse and avoid immediately applying strong acids or retinols.” As for LED devices, she says it’s okay to use them in conjunction with your normal skin-care routine—but be careful with retinol. “It can make your skin more sensitive,” she says.
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What to do if you mix the wrong two
If you end up accidentally using any of the above ingredient combos at the same time and experience irritation, you’ll want to stop using them until your skin recovers. “If the skin starts to look inflamed or irritated, I generally recommend stopping all products and simply using a gentle cleanser, such as Cetaphil Gentle Skin Cleanser [$10] or Dove, and moisturizer such as Cerave Moisturizing Cream [$18],” Dr. Garshick says. “Calming lotions with ingredients like chamomile, aloe vera, sea buckthorn oil, and even green tea help,” Dr. Shamban adds. “For more extreme cases, topical cortisone is usually required.”
Know how to layer
Not only is it important to know which products work well together, but knowing how to properly layer them is also key. “Give a time-out in between application layers, to allow the product to absorb into the skin,” Dr. Shamban explains. “I would suggest a two-minute-minimum rule, not just slathering on layer on top of layer.” Pro tip: after one layer, brush and floss your teeth or put on an eye cream, to give the products some time to absorb. As a general guideline for layering, Dr. Shamban says you should always use a light liquid, like a toner or serum, that’s water- or hyaluronic-based first. And make sure to use retinoids at night, since they decay in the sun and can make the skin more susceptible to burns.
Bottom line
If you’re adding a new product or ingredient to your routine, pay close attention to how your skin reacts—and don’t rush the process. “It is always best to add one at a time, and often I recommend waiting one week before introducing a new product. This gives the skin a chance to get used to it, and if any reaction were to occur, you would know what it’s from,” Dr. Garshick says.
