Vitamin C

What can’t vitamin C do? Its skin benefits are vast—the antioxidant can lighten hyperpigmentation, diminish fine lines, and boost overall radiance, similar to the glow you feel after downing a glass of freshly squeezed orange juice. However, with great skincare ingredients comes great responsibility, and we’re not just talking about how some vitamin C formulas can be less potent than others. For those with sensitive, reactive skin, certain forms of vitamin C can be shockingly irritating, leading to dryness, peeling, and redness.

But you shouldn’t bin your vitamin C serums or moisturizers right after reading that. According to Klur founder Lesley Thornton, it all comes down to the science that happens on your face during your skincare routine.


“There is a lot of chemistry involved here; there is the formula’s pH, the skin’s pH, and the relationship between the two,” Thornton explains. “The form of vitamin C most likely to cause irritation in people with sensitive skin is L-ascorbic acid (L-AA). For L-AA to be stable in water, it must be formulated at a very low pH. This extremely acidic pH offers maximum formula stability, but limited skin compatibility; thus enhancing its exfoliating properties and weakening barrier function, which is why many sensitive skin types may peel, turn red, and have other adverse reactions.”

It’s a bit like a math equation: the more potent the form of vitamin C, the more irritating for those with sensitive skin. Other factors or ingredients that might seem beneficial at first can also amplify the effect. “Higher percentage products may be more irritating,” says Dr. Kristina Goldenberg of Goldenberg Dermatology. “Products that are combined with other acids, such as alpha hydroxy acid, can be more irritating.”

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This sounds simple, but these important pieces to the facial puzzle can be glossed over in our rush for picture-perfect skin as quickly as possible. And it doesn’t hurt to introduce any vitamin C product into your routine gently, treating it like the powerful ingredient that it is. “It is possible to start with a lower concentration of vitamin C and work your way up,” says SkinCeuticals partner dermatologist Dr. Kim Nichols. “I recommend that people start with a serum that has a lower concentration of vitamin C, like 10 percent, and then increase to a 15 to 20 percent serum over time as their skin gets used to it. In addition, when introducing any new skincare product into your routine, it is always best to start slow by either doing a patch test or applying two to three times a week at first.”

And it’s worth reading up on the different types of vitamin C if L-AA doesn’t work with your skin. Thornton suggests sodium ascorbyl phosphate or tetrahexyldecyl ascorbate, while both Nichols and Thornton recommend magnesium ascorbyl phosphate for sensitive skin.

Thornton notes that magnesium ascorbyl phosphate remains highly stable in water— “which makes for more elegant formulations, no sticky stuff,”—while being a relatively weak derivative. “However, studies show it still offers the collagen-boosting benefits of L-AA and is a viable option for someone who is interested in exploring derivatives and gentle vitamin C alternatives,” she continues.

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The last big thing to remember here, though, is that not everyone has sensitive skin and will run into these issues. Thornton points out three potential reasons why skin can experience vitamin C irritation: a weak skin barrier could be at play here, your skin might not be able to handle extreme pH level shifts, or it might not be able to re-adjust its pH level quickly enough after application, thus disrupting the delicate system.

So, how can you predict how your skin will react, or find out what’s causing any redness or irritation? Phone a friend…ly dermatologist. “If you find your skin getting irritated with something in your skincare routine, the best thing to do is visit your board-certified dermatologist to help narrow down the cause of the irritation,” adds Nichols. That way, you’ll have a better understanding about which type of vitamin C works best for your skin before you splurge on any luxury formula.

This article originally appeared on Harper’s BAZAAR US.

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