Skin-Care Ingredients You Shouldn’t Mix

Vitamin C, retinol, salicylic acid, glycolic acid, peptides — the list of buzzy skin-care ingredients goes on and on. With so many new product formulations and ingredient advancements popping up left and right, it can be hard to keep track of what can and cannot be used together. To give you a lesson in skin-care ingredients 101 and prevent irritation, we spoke with board-certified dermatologist and Skincare.com consultant Dr. Dendy Engelman.

Skin-Care Ingredients That Shouldn’t Be Used Together

Don’t Mix Retinol + Acne Treatments (Benzoyl Peroxide, Salicylic Acid)

The phrase less is more is very applicable here. “With the exception of Epiduo (which is prescription treatment specifically formulated to co-exist with retinol), benzoyl peroxide and beta-hydroxy-acids (BHAs) like salicylic acid shouldn’t be used with retinoids,” says Dr. Engelman. When they are, they deactivate each other, making them ineffective. If you are looking to add a benzoyl peroxide face wash into your routine on its own, though, we recommend the CeraVe Acne Foaming Cream Cleanser. 

Don’t Mix Retinol + Glycolic or Lactic Acid 

Retinols and retinoids, like the La Roche-Posay Effaclar Adapalene Gel, and alpha-hydroxy-acids (AHAs), like the L’Oréal Paris Revitalift Derm Intensives Pure Glycolic Acid Serum, shouldn’t be combined as they can dry out your skin and increase its sensitivity. “It is important to avoid using too many active products that could be overworking the skin and breaking down the bonds of healthy cells,” says Dr. Engelman. “There is, however, no evidence to support them deactivating each other.”

Don’t Mix Retinol + Sun (UV rays)

Retinol is so effective because it increases cellular turnover on the skin’s surface, revealing younger cells. With this in mind, Dr. Engelman advises taking extra precautions in the sun. “New skin can easily be irritated or sensitive when exposed to harsh UVA/UVB rays.” This is another reason retinol should be used at night before bed instead of in the morning, when skin is more likely to be exposed to sunlight. For a great daytime sunscreen and moisturizer duo, we suggest the Vichy Aqualia Thermal UV Defense Moisturizer With SPF 30. 

Don’t Mix Citric Acid + Vitamin C

Vitamin C is a potent antioxidant that is known to help visibly brighten the skin. One of our favorite vitamin C products is the SkinCeuticals C E Ferulic Serum. But when used with citric acid, which promotes skin peeling, the ingredients can destabilize each other. 

“Over-exfoliation will expose skin, weaken skin-barrier function and could trigger inflammation,” says Dr. Engelman. If the barrier function is damaged, skin becomes vulnerable to infection from microorganisms, such as bacteria and fungus, and leads to sensitivity and irritation.”

AHAs + BHAs

“AHAs are best for dry skin and anti-aging, while BHAs are best for addressing the appearance of acne such as large pores, blackheads and pimples,” says Dr. Engelman. But combining AHAs, like glycolic acid, and BHAs, like salicylic acid, can be harsh on the skin. “I have patients who start using exfoliating pads (that contain both types of acid) and the results after the first use are so amazing that they use it every day. By day four, they come to me with dry, irritated skin and they blame the product.” 

The best way to avoid skin sensitivity when it comes to exfoliating is to start out slow, only using the product once a week, and building up frequency as your skin adjusts. “Over-treating the skin makes matters worse because excessive exfoliation can breakdown the stratum corneum, whose job is to be a barrier against pathogens,” says Dr. Engelman. “Even if the barrier function isn’t visibly damaged, the skin may experience a low amount of inflammation (called chronic inflammation), which over time prematurely ages skin.”

Don’t Mix Vitamin C + AHAs/Retinol

Because AHAs and retinoids chemically exfoliate the skin’s surface, they shouldn’t be combined with vitamin C at the same time. “When used in conjunction, these ingredients cancel out the effects of one another or can be irritating to the skin, causing sensitivity and dryness,” says Dr. Engelman. "Vitamin C acts as an antioxidant and AHA chemically exfoliates, together these acids destabilize each other." Instead, she recommends using vitamin C in your morning routine and AHAs or retinol at night.

Skin-Care Ingredients That Work Well Together 

Do Mix Green Tea and Resveratrol + Glycolic or Lactic Acid

Thanks to the anti-inflammatory properties in green tea and resveratrol, they pair well with AHAs. When used together, green tea or resveratrol can have a calming effect on the skin’s surface after exfoliation, according to Dr. Engelman. Want to try this combination? Use the SkinCeuticals Glycolic Renewal Cleanser and the PCA Skin Resveratrol Restorative Complex. 

Do Mix Retinol + Hyaluronic Acid

Because retinol can be slightly irritating and drying on the skin, hyaluronic acid can be a skin-saver. “Hyaluronic acid helps to hydrate the skin, combatting both the irritation and peeling,” says Dr. Engelman. For an affordable hyaluronic acid serum, try the L’Oréal Paris Revitalift Derm Intensives Pure Hyaluronic Acid Serum.

Do Mix Benzoyl Peroxide + Salicylic or Glycolic Acids

Benzoyl peroxide is great for treating acne, while hydroxy acids are helpful in breaking down clogged pores and blackheads. Dr. Engelman explains it like this: “Using benzoyl peroxide is essentially like dropping a bomb to eradicate any acne and bacteria on your skin’s surface. Together, they can effectively treat acne.”

Do Mix Peptides + Vitamin C

“Peptides help to hold cells together, while vitamin C works to reduce environmental stress,” says Dr. Engelman. “Together, they create a barrier for the skin, lock in moisture and ultimately work to improve texture long term.”

Do Mix AHA/BHAs + Ceramides

Adding a restorative, hydrating ingredient to your skin-care routine whenever you’re exfoliating using AHAs or BHAs is key. “Ceramides help to restore the skin’s barrier by holding the cells. They lock in moisture and act as a barrier against pollution, bacteria and assailants,” says Dr. Engelman. “After using chemical exfoliants, you must add moisture back into the skin and protect the skin barrier, and ceramides are an effective way to do that.” For a nourishing, ceramide-based cream, we recommend the CeraVe Moisturizing Cream. 

Photo: Chaunte Vaughn

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