Active ingredients in skincare abound these days — if you want to diminish fine lines, use a product with vitamin C; salicylic acid combats acne; hydroquinone is an effective brightener — and as most consumers are looking to target more than one skin issue at a time, layering or combining products is a common practice. (In Korea, women are known to layer as many as seven products at a time.)
But mixing actives may not be the best course of action if they aren’t already compounded in one product, experts say.
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“Active ingredients are what make a product effective — everything else, whether it’s an oil, cream or gel formulation, is a vehicle to deliver the active,” says Dr. Lisa Kellett, dermatologist at DLK on Avenue in Toronto. “The problem with mixing the wrong ones is that they can turn into potential irritants and cause an allergic reaction. But they can also cancel each other out, making them ineffective.”
We broke down some common potential active ingredient combinations that you could be guilty of creating, and explain how they could be wreaking havoc on your skin.
#1 Retinol + Vitamin C
Both retinol (which is a vitamin A derivative) and vitamin C are effective in combatting the signs of aging, including fine lines, firmness and uneven skin tone. But using them together can be very irritating to the skin.
“This combination could exacerbate already sensitive skin,” Kellett says, and a reaction like that could set your anti-aging goals back considerably by making your skin look older. “Both are treatment-based regimens and should be used independently.”
Since vitamin A can make skin more photosensitive, it’s best used at night, while vitamin C isn’t reactive to sunlight, making it ideal for daytime use.
#2 Oil-based + Water-based Skincare
It’s simple science, really: oil repels water. But when it comes to skincare, oil will also prevent water-based formulas from penetrating the skin.
“You can get away with it if you’re using a water-based cleanser with an oil-based moisturizer, but oil will leave a film on your skin, so if you apply a water-based product on top, it will considerably decrease the absorption of it,” Kellett says.
#3 Benzoyl Peroxide + Hydroquinone
With this ingredient mix — benzoyl peroxide is effective for acne, while hydroquinone is a skin lightening agent — you’re headed straight for a seriously skin-irritating outcome.
Not only that — by mixing the two, you run the risk of staining your skin. Don’t worry if it happens, though — the effect can be removed with soap and water.
#4 Salicylic Acid + Glycolic Acid
While one ingredient is a popular acne treatment, and the other an effective exfoliant that helps diminish the appearance of sun and age spots, mixing the two will strip your skin.
“Both actives are keratolytic agents that help to remove dead skin cells from the stratum corneum ,” Kellett says. “Use them both and you’ll double-blast your skin and have an irritant reaction.”
#5 Sunscreen + Anything, really
“I always tell my patients that the most important product goes on first, so start with sunscreen,” Kellett says. The only problem is that it will decrease your skin’s ability to absorb any subsequent products.
She tells patients to follow up with a moisturizer that will act as an emollient to prevent skin from getting too dry, but save your more precious potions for later.
“When you get home at the end of the day and are staying in for the night, wash your face and use one treatment , and then wash your face again before bed and do another treatment ,” Kellett says. “If you get home around five and go to bed at 11, that gives you six hours with one treatment and eight hours with another.”
It’s also not a good idea to mix sunscreen into your moisturizer or foundation, as they could break down its effectiveness.
At the end of the day, common sense should reign when you’re combining products. If you notice your skin is reacting adversely, slowly take products out of the mix to try to determine the irritant. And if all else fails, see a dermatologist who can help you establish a routine that will target your issues and get you back on the road to healthy skin.
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