There's one active ingredient that dermatologists wax lyrical about. But how to use vitamin C in your skincare routine still causes confusion.
The first question to address is the age at which you should start using vitamin C regularly. “I usually recommend people start in their 30s, when natural antioxidant defences in the skin start to decline,” says Joshua Zeichner, MD, associate professor of dermatology at Mount Sinai Hospital in New York City.
The effort will pay off as vitamin C boasts a multitude of skin-friendly benefits. One of its key traits is brightening skin. “It blocks a key enzyme involved in the production of excess melanin,” explains Dr. Zeichner, which is why it’s able to treat those hyperpigmentation blemishes so effectively. Vitamin C-based serums can also help to boost collagen production and improve the look of fine lines.
Keep scrolling to discover exactly how to use vitamin C in your routine for a next-level glow and what ingredients you shouldn’t mix with this active…
The best vitamin C serums, at a glance
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When should vitamin C be used in your skincare routine?
You should take vitamin C year-round. But winter is a good time to start using a serum powered by this active, as it's an antioxidant (antioxidants help to neutralise free radicals, which help protect the skin from environmental damage, Dr. Zeichner explains). Even though free radical damage can happen all year long, it's especially common during the summer months due to increased exposure to UV rays from the sun.
Dr. Zeichner recommends applying vitamin C in the mornings to protect your skin and prevent environmental damage. After washing your face with a gentle cleanser, apply a few drops of vitamin C serum.
You’ll find many of these products are boosted with additional hydrating ingredients, so moisturiser is optional depending on your skin type. However, what's non-negotiable is using a broad-spectrum sunscreen that's at least an SPF30 to defend against UV rays. And you can wear a vitamin C serum under foundation, so feel free to finish up your makeup routine after that.
If you prefer to use a vitamin C serum before bed, you'll be reassured to know that “there is data to suggest that applying vitamin C at night is also beneficial to the skin, as UV light damage can have long-lasting effects even hours after exposure,” says Dr. Zeichner. You would apply your vitamin C serum in much the same way as in the mornings, but skipping the final SPF stage.
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What shouldn’t you mix with vitamin C?
Though vitamin C is part of a gold-standard anti-ageing skincare routine, you want to be conscious of how you're using it. The powerful antioxidant can come with side effects: “It has the potential to cause skin irritation,” says Dr. Zeichner.
A good rule of thumb is that it “should not be combined with other actives that are also irritating, as the combination may cause a reaction in the skin,” explains Dr. Zeichner. “Avoid layering vitamin C with retinol, hydroxy acids, or benzoyl peroxide.” So if you’re using vitamin C in your morning routine, use your retinol, physical exfoliator, or other exfoliating actives in the evening.
If you have sensitive skin or are experiencing irritation or redness on your face, consider using these actives less often, like three times per week, and gradually build up tolerance. “It is okay to use vitamin C daily, so long as you are not irritated by it,” he says. “If you develop redness, burning, or stinging, hold off a day or two.”
Seeing multi-ingredient formulations on the market? If you see vitamin C plus an exfoliating acid or other active ingredient in the same product, don't panic. Instead, take note that some may be formulated this way “to offer synergistic benefits, but these products have been pre-formulated and safety-tested,” says Dr. Zeichner. “When separate products are combined, especially at higher concentrations, they are more likely to cause irritation.”
Ingredients like ferulic acid, hyaluronic acid, vitamin E, and niacinamide also often sit alongside vitamin C in the same bottle to help boost the effects or provide additional hydration.
How do you choose a vitamin C serum?
In skincare products, topical vitamin C comes in two forms: as pure ascorbic acid or in its ester form, explains Dr. Zeichner. “Pure ascorbic acid is more potent but more unstable and potentially irritating,” he says. If your skin has a high tolerance for vitamin C, or you want stronger antioxidant power, look for ascorbic acid or l-ascorbic acid on the label.
Meanwhile, “vitamin C esters like sodium ascorbyl phosphate and other compounds with the word ascorbyl in them are more stable and better tolerated but less potent,” he says. “They need to be converted into the active ascorbic acid by the skin after application.” He recommends dry and sensitive skin types use vitamin C esters.
As much as we love our vitamin C, the skincare ingredient can be a finicky one sometimes. “Pure vitamin C is a very temperamental ingredient that can easily be inactivated,” says Dr. Zeichner. Make sure your vitamin C serum comes in a dark or opaque bottle: “Pure ascorbic acid is particularly sensitive to changes in pH, temperature, and UV light. This is why pure ascorbic acid comes in opaque bottles, as UV will inactivate the molecule.”
As with sunscreen, pay attention to the expiration date on the bottle. “The formulas tend to turn orange as the vitamin C oxidises,” Dr. Zeichner says. “If you have a formula that does not look, smell, or feel as it did when you purchased it, toss it.”
Here are some of the best vitamin C serums we tested:
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A version of this article originally appeared on US Glamour.
