Beauty The Dos and Don'ts of Mixing Skincare Ingredients Plus, when and how to use them. By Erin Lukas Erin Lukas Instagram Twitter Erin is a Brooklyn-based beauty editor and has been with InStyle since 2016. She covers all facets of beauty for the site. InStyle's editorial guidelines Updated on August 21, 2022 @ 11:30AM Pin Share Tweet Email Photo: Layla Bird / Getty Images So, you're new to skincare. Or, maybe you've decided it's time to take your routine to the next level with more than just a simple cleanser and moisturizer. Either way, you've done the research, read some online reviews, and stocked up on products in your budget that will treat your main areas of concern. Now, you just need to figure out whether the ingredients in all of these creams, serums, and masks work harmoniously. Welcome to skincare mixology 101. Second to picking formulas for your skin type and issues, it's important that all of the products in your routine complement one another so you can actually see results. "Mixing ingredients without proper knowledge of how these ingredients work and what other ingredients they may interact with will be not only a waste of money but also time. It can also lead to frustration if less than expected results are seen (or if the skin becomes irritated)," says Dr. Shari Marchbein, a board-certified dermatologist in New York City. The Exact Order You Should Apply Your Skincare Products — Morning and Night Skin irritation is another big factor to consider when curating the product lineup in your skincare routine. "Your skincare routine should include products that complement each other in order to avoid over-drying, over-exfoliating, or irritating the skin," adds Dr. David Lortscher, board-certified dermatologist and CEO of Curology. "More is not always better." With the help of both dermatologists, we've put together a complete guide on the dos and don'ts of mixing and matching the most popular skincare ingredients found in products. Retinol Ah, retinol. It's one of the most revered skincare ingredients that dermatologists love to recommend. Also known as vitamin A, what makes retinol so great is that it promotes skin cell turnover, which can help improve the appearance of fine lines, wrinkles, uneven skin texture, dark spots, and acne. The only catch? Retinol can be extremely irritating. "Retinol is an effective anti-aging ingredient, but can exacerbate skin dryness," explains Dr. Lortscher. Do Mix: Retinol with moisturizing ingredients like hyaluronic acid and ceramides as well as SPF. "Make sure to moisturize; humectant ingredients like hyaluronic acid can draw and hold water molecules to the surface layers of your skin, while oil-based emollient ingredients help seal in moisture." It's also important to keep in mind that retinol can make you more sensitive to the sun. "SPF should be worn religiously every day of the year, not only to prevent skin cancers, wrinkles, and sunspots, but because many other ingredients we apply to our skin including retinol and retinoids can make the skin more sensitive to the sun," says Dr. Marchbein. Every Question You've Ever Had About Retinol, Answered Don't Mix: Retinol with vitamin C, benzoyl peroxide, and AHA/BHA acids. AHA and BHA acids are exfoliating, which can dry out the skin and cause further irritation if your skincare routine already includes retinol. As for benzoyl peroxide and retinol, they cancel each other out. "It is not recommended to use benzoyl peroxide and retinoids together as they can literally cancel each other out rendering them less effective," explains Dr. Marchbein. Finally, because vitamin C protects skin from environmental aggressors and retinol repairs and rebuilds skin, they're best used at opposite times of the day. (More on that in a second.) Vitamin C "Vitamin C protects the skin from oxidative free radical damage and works best in the morning," says Dr. Marchbein. This ingredient also brightens the skin and can even lighten dark spots. Do Mix: Vitamin C with antioxidants and SPF. When vitamin C is used with other antioxidants like vitamin E, it can boost results and efficiency. The same goes for wearing vitamin C under sunscreen. "Vitamin C serums should always be layered under sunscreen because they complement one another and will protect skin against UV damage," explains Dr. Marchbein. Don't Mix: Vitamin C with retinol. In contrast to vitamin C, retinol and retinoids build collagen and help repair the skin, so they're best used overnight. Since vitamin C thrives in the daytime, it's best to keep these ingredients separate from each other because they have such different functions. All of the Benefits of Using Vitamin C in Your Skincare Routine AHA/BHA Acids Salicylic, glycolic, and lactic acids are all effective exfoliants that can improve skin texture, tone, and in the case of SA, treat acne. That being said, all three of these acids can dehydrate and irritate the skin. The bottom line: When using products with AHA or BHA acids, follow up with a hydrating product. Do Mix: AHA/BHA acids with moisturizing ingredients and SPF. "Moisturizing after applying AHA and BHA is extremely important so as to limit irritation. Look for ceramides, petrolatum, hyaluronic acid, and glycerin to hydrate and soothe skin," says Dr. Marchbein. Using a product that combines multiple low-level AHA and BHA acids can be an extremely effective way to exfoliate and unclog pores. Like retinol, AHA/BHA acids can cause sun sensitivity. While you should be wearing sunscreen every day regardless of what products are in your skincare routine, it's extra important to not skip this step when you're using these ingredients. Don't Mix: AHA/BHA acids with retinol. "I strongly caution those also using retinoids for acne or anti-aging as the combination with various acids may cause excessive skin sensitivity, irritation, and redness. In fact, AHA and BHA should not typically be used together with retinoids on the same day," explains Dr. Marchbein. "Also, be careful combining various acids or even physical and chemical exfoliants, as this can lead to irritation and even eczema." Benzoyl Peroxide Benzoyl peroxide can be a game-changing addition to your skincare routine if you have acne-prone skin. The caveat? It's another drying ingredient. "Because acne treatments, in general, can cause dryness and irritation of the skin, combining them together needs to be done with caution and every other part of the skincare routine (i.e. cleanser and moisturizers) need to be extremely gentle and ultra-hydrating, respectively," explains Dr. Marchbein. Do Mix: Benzoyl Peroxide with gentle hydrating ingredients, SPF, and topical antibiotics. Along with moisturizing ingredients that can buffer the dehydrating effects of benzoyl peroxide, the acne-fighting component can be used in conjunction with prescription topical treatments like clindamycin. SPF should also be worn every day. The Best Skincare Routine for Acne, According to Dermatologists Don't Mix: Benzoyl peroxide with retinol, acne prescription tretinoin with caution. As previously mentioned, benzoyl peroxide and retinol can deactivate one another when used together. While prescription acne treatments can be used with BP, tretinoin requires extra care. Dr. Lortscher explains: "Depending upon how the product is formulated, benzoyl peroxide may inactivate tretinoin somewhat if they are mixed together in the same bottle. They do appear to work just fine in our experience when applied to the skin one after the other — and it does not matter in which order, just rub one product in gently and completely before applying the other," he says. "If you want to minimize any chance of interaction if you are using tretinoin, apply the tretinoin-containing formulation in the PM, and use your benzoyl peroxide in the AM, or use a wash-off benzoyl peroxide cleanser rather than layering a leave-on benzoyl peroxide." VIDEO: Beauty Now: Facial Acupuncture Niacinamide Otherwise known as vitamin B3, this antioxidant is an anti-inflammatory that can brighten skin and even out discoloration. Do Mix: Niacinamide with (almost) every ingredient in your skincare routine. "Because niacinamide is anti-inflammatory, the skin reacts very minimally to it, and side effects such as irritation are unusual," Dr. Lortscher explains. "It should be compatible with most other skincare products, and for best results, use a leave-on product such as a moisturizer." Don't Mix: Niacinamide and vitamin C. Although they're both antioxidants, vitamin C is one ingredient that's not compatible with niacinamide. "Both are very common antioxidants used in a variety of skincare products, but they should not be used one right after the other," says Dr. Marchbein. "Their potency is significantly diminished when used together, unless the application is spaced by at least 10 minutes between each serum." SPF If you're going to use one skincare product, make it SPF. It's the only way to effectively protect skin from cancer and environmental aggressors, which can lead to premature signs of aging. Given its importance, SPF can be layered over any skincare ingredient. Do Mix: SPF can (and should) be used in any and every skincare routine. Don't Mix: SPF with makeup or moisturizers. Yes, SPF can feel like an extra step in an already-extensive skincare routine, but don't try to take shortcuts. "Don't mix your sunscreen with your makeup or moisturizer and apply as on — sunscreen should be applied as a single layer to preserve the protective factors," says Dr. Lortscher.