Retinol and Vitamin C
Although retinol and vitamin C are commonly used ingredients to help improve fine lines, texture, and brown spots, using them at the same time can reduce their efficacy, according to Dr. Pierre. "Retinol and vitamin C are designed to work at different pH levels," he says. "To get the most out of each product, try to use vitamin C in the morning and your retinol in the evening."
Retinol and Benzoyl Peroxide
Retinol and benzoyl peroxide are both effective treatments for acne, according to Dr. Pierre, as they both work hard to unclog pores from pimple-causing bacteria.
That said, using them at the same time can spell out trouble for your skin, as doing so can cause unwanted irritation, redness, and flaking. "To avoid unwanted reactions, it's better to reserve benzoyl peroxide for the morning (be aware that it can bleach clothing!) and retinol for the evening," explains Dr. Pierre.
Sunscreen, Makeup, and Moisturizers
While it's perfectly reasonable to layer makeup or moisturizing products on top of sunscreen (which we hope you are using btw!), Dr. Pierre says you'll want to layer your products carefully, as some products can reduce the effectiveness of your SPF protection.
Instead, he suggests finding makeup and moisturizing products (looking at you, tinted moisturizer!) with built-in SPF protection. He explains that this helps to ensure that you are properly protected throughout the day.
Vitamin C and Niacinamide
Vitamin C and niacinamide are great ingredients when it comes to pigmentation issues, according to board-certified dermatologist Dr. Jason H. Miller, MD. But... don't mix them: "Both vitamin C and niacinamide are great for correcting redness and uneven skin tone," he explains. "However, they can cancel each other out if applied together."
Vitamin C and AHA/BHA
Yes, a supercharged vitamin C serum and AHA/BHA mask may seem like the dream team duo you need to achieve that #nofilter glow... however, Dr. Pierre and Dr. Miller both caution that they generally shouldn't be mixed.
"Aside from potential tolerability issues and the potential of causing a lot of irritation, these acids can destabilize vitamin C, and significantly decrease its effectiveness," he explains. "It's best to use vitamin C products in the morning, and then relegate your AHA/BHA product in the evening." Dr. Miller agrees, adding "Vitamin C acts as an antioxidant, and AHA acts to exfoliate, but they can also deactivate each other."
