How to Use Vitamin C in Your Skin-Care Routine Correctly, According to the Experts

You may have been taught that Vitamin C should be the first step in your everyday skin-care routine—but dermatologist Ana Santamarina argues that you should still rethink your everyday application, because certain Vitamin C formulas last longer than others. “Pure Vitamin C creates a reservoir in the skin,” she says. “It can accumulate for up to three or four days, so its daily use would not be necessary, as long as the Vitamin C has certain characteristics.”

But beware: this cannot be done with all formulations. According to Santamarina, it has to be a product with 10 to 15% ascorbic acid at a pH of 3.5 or lower. “This way it can accumulate in the tissues for up to four days, which means it could be used three or four times a week,” she says. In fact, the study Topical L-Ascorbic Acid: Percutaneous Absorption Studies conducted by Dr. Sheldon R. Pinnell found that a 15% ascorbic acid formulated at a pH of 3.2 had a half-life on the skin of about four days.

Experts recommend a serum higher than 8%, with a gold standard of around 12%, but Santamarina underscores that the pH must also be taken into account. “Concentration is not always the most important thing, nor is it what makes the active ingredient more or less bioavailable and effective,” she continues. “It is a combination of factors such as pH and sun protection. The main drawback of pure Vitamin C is its instability. This can happen in contact with an alkaline pH and in contact with air or light.”

If you choose an ampoule or serum with Vitamin C formulated with 10 to 15% ascorbic acid at a pH of 3.5 or lower, you could use this active ingredient alongside others to help protect the skin. An option for those days when Vitamin C is not used could be niacinamide. “It’s an antioxidant and also improves skin tone,” Santamarina says. Plus, it’s great for all skin types and an anti-inflammatory.

Although it’s a popular ingredient, the reality is that Vitamin C isn’t for everybody. There are other antioxidant formulas that can help in a similar way. “The good reputation of Vitamin C is indeed justified, but I meet people for whom it doesn’t work as well, and they still insist. Of course, you can try different formulas, but as I always tell them, ‘Maybe this active is not for you and we can look for another that is better suited to your skin,’” Santamarina says.