Skincare can be a minefield. There's identifying skin type (oily, dry, combination), its concerns (acne, pigmentation, hydration), and of course, the best products for you. Above all, however, when seeking results from said products, you need to prioritise best practice, because if you're not using your products properly, they can become redunant – or worse, you could be faced with adverse effects like irritation, dryness and flaking. Not cute!
One major factor to consider in best skincare practice is mixing certain ingredients together – or rather, which ingredients you should not mix together. Yep, that's right, some of the most popular ingredients should not be used with each other, like niacinamide and vitamin C.
To find out more, we spoke to dermatologist Dr Ophelia Veraitch, who shared the do's and don't of mixing skincare ingredients below. Notepad and pen at the ready...
The ingredients you should not mix
As mentioned, some active ingredients are fantastic on their own, but when used together, they can overwork or irritate the skin. "A classic example is retinol with AHAs (alpha hydroxy acids) or BHAs (beta-hydroxy acids). Both have exfoliant actions on the skin, so layering them can easily cause redness and peeling," Dr Ophelia says. This goes the same for when too many potent actives are combined. Doing so can compromise your skin barrier, resulting in dryness, stinging, or flaking, aka, the opposite of what you're trying to achieve.
Similarly, vitamin C is an ingredient that needs to be used with consideration. "If used with acids (like glycolic or salicylic acid), the vitamin C can destabilise reducing its effectiveness," says Dr Ophelia. "It’s also worth being cautious with niacinamide and pure vitamin C (ascorbic acid) – in older formulations, they could neutralise each other and irritate sensitive skin," she adds.
Also, Dr Ophelia warns against using benzoyl peroxide and retinol together; "benzoyl peroxide oxidises retinol, making it less effective."
Everyone's clicking on...
Your 'do not mix' cheat sheet:
AHAs + BHAs
Vitamin C + any acid
Niacinamide + pure vitamin C
Retinol + benzoyl peroxide
The best approach
Naturally, if you have more than one skin concern, you may want to use multiple ingredients. The solution? Alternate using ingredients between days or at different times of day in order to not irritate the skin/dull the product's effectiveness. For example, you could use vitamin C in the morning and retinol at night, or exfoliating acids one evening and retinol the next.
Not to complicate things further, but this is all to say that timing matters. "Vitamin C is best used in the morning because it’s an antioxidant, so it helps protect the skin against free radicals and environmental damage throughout the day," Dr Ophelia says.
Retinol, on the other hand, is best used at night. "It increases cell turnover and can make the skin more sensitive to sunlight, so using it before bed allows it to work while your skin repairs itself overnight," she says.
In short, we always recommend reading the instructions on your products to understand not only how but when they're best used! And if you are experiencing any irritaion, assess any newness in your routine and strip it back to the basics. Sometimes, more is not more!
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Lia Mappoura (she/her) is the Beauty Writer at Cosmopolitan UK, with over four years of experience reporting across the brand's print, social, video and digital platforms. Lia covers everything from emerging trend analysis to viral celebrity hair and makeup moments, making her an expert at spotting the season’s next big beauty look (before it takes over social media feeds).
In 2025, she was named The Rising Media Star at the Love Perfume Awards with The Perfume Shop, recognised for her outstanding digital fragrance content and for building genuine authority within the space. She is passionate about challenging outdated beauty stereotypes, championing inclusive representation in beauty, and educating readers on the trends, products and conversations shaping the industry today. Follow her on Instagram or find her on LinkedIn.
