Skin Care Ingredients You Shouldn't Mix

retinol, Vitamin C, salicylic acid, glycolic acid, peptides - list of popular skin care ingredients goes on and on. With so many new product formulas and improved ingredients popping up left and right, it can be hard to keep track of which ingredients can and cannot be used together. To find out which skincare ingredient combinations to avoid and which together work wonders, we spoke with Dr. Dandy Engelman, NYC Certified Dermatologist and Skincare.com Consultant.

Skin care ingredients that should not be used together

Do not mix retinol + acne products (benzoyl peroxide, salicylic acid)

Phrase less - more very applicable here. "With the exception of Epiduo (it's a prescription drug specifically designed to coexist with retinol), benzoyl peroxide and beta hydroxy acids (BHAs) such as salicylic acid should not be used with retinoids," says Dr. Engelman. When they are, they deactivate each other, rendering them ineffective. However, if you are looking to add a benzoyl peroxide face wash to your routine, we recommend CeraVe Acne Foaming Cream Cleanser.

Do not mix retinol + glycolic or lactic acid. 

Retinol, like Kiehl's Micro-Dose Anti-Aging Retinol Serum with Ceramides & Peptides, and alpha hydroxy acids (AHAs) such as L'Oréal Paris Revitalift Derm Intensives 5% Glycolic Acid Toner, should not be merged. Combined, they can dry out the skin and increase its sensitivity. "It's important to avoid using too many active products, which can overwork the skin and disrupt the bonds between healthy cells," says Dr. Engelman. "However, there is no evidence that the ingredients deactivate each other."

Do not mix retinol + sun (UV rays)

Retinol is so effective because it increases cellular turnover at the surface of the skin, revealing younger cells. With that in mind, Dr. Engelman advises taking extra precautions in the sun. “New skin can be easily irritated or sensitive when exposed to harsh UVA/UVB rays,” she says. This is why retinol should be used in the evening before bed rather than in the morning when the skin is more exposed to the sun. For a great daytime SPF, we suggest SkinCeuticals Daily Brightening UV Defense Sunscreen SPF 30. It contains 7% glycerin to help draw moisture into the skin, as well as niacinamide and tranexamic acid to even out skin tone. 

Do not mix citric acid + vitamin C

Vitamin C is a powerful antioxidant known to help visibly brighten skin. One of our favorite vitamin C foods is IT Cosmetics Bye Bye Dullness Vitamin C Serum. But when used with citric acid, which promotes skin flaking, the ingredients can destabilize each other. 

"Excessive exfoliation exposes the skin, weakens the skin's barrier function, and can cause inflammation," says Dr. Engelman. “If the barrier function is damaged, the skin becomes vulnerable to infections caused by microorganisms such as bacteria and fungi and becomes prone to sensitivity and irritation.”

Don't Mix AHA + BHA

“AHAs are best for dry skin and anti-aging, while BHAs are best for treating acne like enlarged pores, blackheads, and pimples,” says Dr. Engelman. But the combination of AHAs like glycolic acid and BHAs like salicylic acid can have negative effects on the skin. “I have patients who start using exfoliating pads (containing both types of acids) and the results after the first use are so amazing that they use them every day. On the fourth day, they come to me with dry, irritated skin and blame the product." 

The best way to avoid skin sensitivity when it comes to exfoliation is to start slowly, using the product only once a week, and increase the frequency as your skin adjusts. “Over-treatment of the skin exacerbates the situation because excessive exfoliation can destroy the stratum corneum, whose job it is to be a barrier against pathogens,” says Dr. Engelman. “Even if barrier function is not visibly damaged, the skin can experience minor inflammation (called chronic inflammation) that ages the skin prematurely over time.”

Don't Mix Vitamin C + AHA/Retinol

Since AHAs and retinoids chemically exfoliate the surface of the skin, they should not be combined with vitamin C at the same time. “When used together, these ingredients cancel each other’s effects or can irritate 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 AHA or retinol at night.

Skin care ingredients that work well together 

Mix Green Tea and Resveratrol + Glycolic or Lactic Acid

Due to the anti-inflammatory properties of green tea and resveratrol, they pair well with AHA. When used together, green tea and resveratrol can have a soothing effect on the surface of the skin after exfoliation, according to Dr. Engelman. Would you like to try this combination? Use IT Cosmetics Bye Bye Pores Glycolic Acid Serum и PCA Skin Resveratrol Restorative Complex. 

Mix Retinol + Hyaluronic Acid

Since retinol can slightly irritate and dry out the skin, hyaluronic acid can save the skin. “Hyaluronic acid helps hydrate the skin while combating both irritation and flaking,” says Dr. Engelman. For an affordable hyaluronic acid serum, try Garnier Green Labs Hyalu-Aloe Hydrating Serum-Gel.

Mix benzoyl peroxide + salicylic or glycolic acid.

Benzoyl peroxide is great for treating acne, while hydroxy acids help break down clogged pores and clear blackheads. Dr. Engelman explains it this way: “Using benzoyl peroxide is essentially like dropping a bomb to destroy any pimples and bacteria on the surface of your skin. Together, they can effectively treat acne.” La Roche-Posay Effaclar Anti-Aging Pore Minimizer Facial Serum combines glycolic acid with alpha hydroxy acids derived from salicylic acid to minimize sebum production and smooth skin texture. 

Mix Peptides + Vitamin C

"Peptides help hold cells together, while vitamin C reduces environmental stress," says Dr. Engelman. “Together, they create a skin barrier, lock in moisture, and ultimately improve texture in the long run.” Enjoy the benefits of both ingredients in one product with Vichy LiftActiv Peptide-C Ampoule Serum.

Mix AHA/BHAs + Ceramides

The key is to add a revitalizing, hydrating ingredient to your skin care routine whenever you exfoliate with an AHA or BHA. “Ceramides help rebuild the skin barrier by holding on to cells. They retain moisture and act as a barrier against pollution, bacteria and attackers,” says Dr. Engelman. “After using chemical exfoliants, you need to rehydrate your skin and protect the skin barrier, and ceramides are an effective way to do that.” For a nourishing cream based on ceramides, we recommend CeraVe Moisturizing Cream.