Everything You Need to Know About Sodium Ascorbyl Phosphate

Curated by Claudia Shannon / Research Scientist / ishonest

Dermatologists say this gentler form of vitamin C offers a host of different benefits for your complexion.

Sodium Ascorbyl Phosphate

TYPE OF INGREDIENT: Antioxidant

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MAIN BENEFITS: Neutralizes skin-damaging free radicals, boosts collagen production, evens skin tone, has antimicrobial benefits.

WHO SHOULD USE IT: In general, because this is less potent than other forms of vitamin C, it’s generally safe for all skin types, though some people may experience mild irritation.

HOW OFTEN CAN YOU USE IT: Once to twice daily, although it’s always a good idea to start by using it just a few times per week and gradually increasing the frequency in order to ensure your skin can tolerate it, advises Farber.

WORKS WELL WITH: Other antioxidants, in particular vitamin E and ferulic acid, as well as hydrating ingredients such as hyaluronic acid.

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DON’T USE WITH: Benzoyl peroxide can oxidize vitamin C, and retinols work best at a different pH, says Farber. If both of these are a part of your regimen, use them at different times of the day.

What Is Sodium Ascorbyl Phosphate?

Simply put, it’s a form of vitamin C, technically a salt, explains Carqueville. It’s notably less potent than the more commonly used form, l-ascorbic acid. “I think of l-ascorbic acid as the equivalent of lifting a ten pound weight, and sodium ascorbyl phosphate as a five pound weight,” says Gohara. "It's lighter and less intense, though still beneficial.” L-ascorbic acid is the bioactive form of the vitamin, a fancy of way saying it's the form that your skin can actually use. Sodium ascorbyl phosphate ultimately converts into ascorbic acid once it's in the skin; this conversion process is what makes it less active and, yes, also less effective. Still, this is also also why it's much less likely to cause irritation, Gohara explains.

The other major benefit? Most forms of vitamin C, l-ascorbic acid in particular, are notorious for being highly unstable, and easily degraded when exposed to light or oxygen. (This is why you'll often hear that it's best to look for vitamin C products housed in dark, opaque bottles.) Not the case here: “Sodium ascorbyl phosphate is considered to be one of the more stable forms of the vitamin and is light-, oxygen-, and water-stable,” says Carqueville. And that makes it not only easier to incorporate into different product formulations, but also means you don't have to worry about it losing its potency.

Benefits of Sodium Ascorbyl Phosphate for Skin

At its core, any type of vitamin C is a top-notch antioxidant, although it delivers other types of benefits as well.

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Fights free radicals: To that antioxidant point, “it works to combat the effects of UV damage by scavenging the free radicals that cause DNA changes and lead to signs of photoaging,” says Farber. (As a quick reminder, exposure to sun and pollution creates free radicals in the skin, which ultimately can cause things such as spots, wrinkles, and sagging.)

Boosts collagen production: Along with those antioxidant properties, sodium ascorbyl phosphate is an ideal anti-aging ingredient, thanks to its ability to stimulate the production of collagen, the protein responsible for strong, youthful skin. (Interestingly enough, ingesting vitamin C can have the same effect.)

Evens out skin tone: Sodium ascorbyl phosphate is a great ingredient for those looking to combat hyperpigmentation or dark spots, says Carqueville. By inhibiting tyrosinase, the enzyme needed to produce melanin (pigment), it can help both fade existing and ward off future discoloration.

Side Effects of Sodium Ascorbyl Phosphate

While the more intense forms of vitamin C can be notoriously irritating, sodium ascorbyl phosphate is a great option for those who can’t tolerate it, says Gohara. Still, it is a very active ingredient, so there is some potential for irritation, particularly for those whose skin is on the super sensitive side.

How to Use It

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To get the most bang for your buck, look for serums with sodium ascorbyl phosphate, which will contain a higher concentration of the ingredient than a lotion or cream. Apply it in the morning, after cleansing, before moisturizer. This is prime-time to reap the antioxidant benefits of the ingredient, as it will combat any free radicals that form due to the sun or pollution you're exposed to throughout the day. You can also look for serums that cocktail it with other antioxidants, or even layer an additional antioxidant serum on top, suggests Gohara. Just be sure to cap off this morning routine with a broad- spectrum sunscreen with at least an SPF 30.

The Best Products With Sodium Ascorbyl Phosphate

Smaoui S, Hilima HB. Application of l-ascorbic acid and its derivatives (sodium ascorbyl phosphate and magnesium ascorbyl phosphate) in topical cosmetic formulations: stability studies. J Chem Soc Pakistan. 2013;35(4): 1096-1102.

Khan H, Akhtar N, Ali A. Fortification of facial skin collagen efficacy by combined ascorbyl palmitate and sodium ascorbyl phosphate. Acta Poloniae Pharmaceutica Drug Research. 2018;75(1): 129-140.

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