Apply vitamin C in the mornings to protect your skin and prevent environmental damage, recommends Zeichner. “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,” he adds, so you may still be able to reap the benefits of the ingredient. However, most people just apply it in the morning as part of their daytime skin care routine.
In the mornings, after washing your face with a gentle cleanser, apply a few drops of your vitamin C serum to your face. You’ll find many of these serums are boosted with additional hydrating ingredients, so if you have super dry skin, follow with a moisturizer and SPF. Some can skip moisturizer and go straight to the SPF (make sure you’re protecting yourself from sun damage by applying a broad-spectrum sunscreen that’s at least SPF 30). You can wear vitamin C serum under makeup, so feel free to finish up your makeup routine after that.
What shouldn’t you mix with vitamin C?
Though vitamin C is part of a gold standard anti-aging skin care 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 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 formulations on the market that contain vitamin C plus an exfoliating acid or other active ingredient? Take note that some may be formulated this way “to offer synergistic benefits, but these products have been pre-formulated and safety tested,” says Zeichner. “When separate products are combined, especially at higher concentrations, they are more likely to cause irritation.” You’ll often see formulas include ingredients like ferulic acid, hyaluronic acid, vitamin E, and niacinamide alongside the vitamin C to help boost the effects or provide additional hydration.
How do you choose a vitamin C serum?
In skin care products, topical vitamin C comes in two forms: as pure ascorbic acid or in its ester form, explains 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.