The No BS Guide to Vitamin C (L-Ascorbic Acid) Serums for Brighter Skin

Not all vitamin C serums are created equal

Whether you’ve been looking to simplify your skin care routine or amp it up, a vitamin C serum might be your golden ticket. Topical vitamin C is a multipurpose workhorse that can protect, repair, and enhance your skin.

But, as with any products, not all serums are created equal. Components like the type and concentration of vitamin C, the ingredient list, and even the kind of bottle or dispenser make or break your serum’s benefits — and your skin.

But don’t worry, decoding which serum to buy isn’t that hard. We’ve got the facts on C serum benefits, how to choose one (plus recommendations), and tips on how to make the most use of them.

The serious benefits of a vitamin C serum and when to apply it

Vitamin C is an antioxidant, meaning it halts or holds off environmental and sun damage to cells. And while you can count your morning OJ as a good defense for your bod, the best way to achieve vitamin C’s protection and benefits is to apply it directly onto your skin.

But there’s also a reason why you don’t want to just be placing citrus slices on your cheeks. When you DIY, there’s no control over the quality — and sometimes it’s not even safe. It’s also just not efficient.

That’s because when we eat, drink, or supplement vitamin C, also known as ascorbic acid, our skin only gets a small fraction of the benefits. However, pressing vitamin C in serum form, after it’s been chemically altered, actually lets our skin absorb more of it in an efficient way.

If you’re wondering when to apply a vitamin C serum, the answer is both morning and night, after cleansing and toning. One study even recommends applying a vitamin C serum every eight hours, or twice daily for the pinnacle of protection.

Vitamin C has photoprotective properties and staves off oxidative stress from the free radicals we meet throughout our day. Think car exhaust, cigarette smoke, certain chemicals, even booze and overprocessed foods.

But don’t worry if you skip an application. Unlike sunscreen, moisturizers, or oils, vitamin C can’t be wiped or washed off that easily.

Vitamin C’s protection and free radical-fighting prowess eventually wears off, but you can build up a reservoir for adequate photoprotection. This can be achieved by applying every eight hours.

Also, UV light lowers the skin’s vitamin C levels. It’s been found that topical vitamin C is best applied after exposure to UV light and not prior.

Always use SPF with vitamin C

Although vitamin C serum isn’t a substitute for sunscreen (in fact, sun sensitivity increases with use), the two together can work in tandem to boost the skin’s protection from damage.

You might be ready to hit the buy button, but choosing a vitamin C serum that will actually go to work for your skin involves a bit of product research. We delved into the science and made some recommendations.

What to look for in a vitamin C serum

Form: Vitamin C can appear on the ingredient label as several different names, but the one you want is L-ascorbic acid, which is the most effective. An older study comparing common vitamin C derivatives with L-ascorbic acid didn’t show an increase in absorption.

Make sure this good-guy ingredient is close to the top of the label, ideally as one of the first five ingredients.

Concentration: The sweet spot for the concentration level is between 10 and 20 percent. You definitely want a concentration that’s higher than 8 percent for maximum effectiveness. But going over 20 percent could lead to irritation and doesn’t increase its benefit.

Patch test with high percentages

Vitamin C is mostly safe to use, but in rare instances, side effects may occur, like stinging, redness, dryness, or a yellowish discoloration. As with any new product, try a patch test first before a full application.

Ingredient: Look for both vitamins C and E, or L-ascorbic acid and tocopherol respectively, on your ingredient list. Think of these skin boosters as besties that do well together.

Vitamin E stabilizes vitamin C for maximum skin protection. Another antioxidant called glutathione also is a good pal to vitamin C.

Then check for ferulic acid, which helps lower the pH level of vitamin C to below 3.5 percent so your skin can easily slurp up the cocktail.

Packaging: Exposure to air, light, and heat can degrade your serum. Look for a product that comes in a dark glass bottle featuring a medicine dropper delivery, rather than an air pump.

A tube also works. Some retailers suggest storing the product in the refrigerator to prolong its shelf life. A thoughtful brand will include label instructions on how to store their serums.

Expiration time

Many serums are yellow, but if your product takes on a brown or dark orange hue, it’s time to toss because it’s gone bad. If your serum starts out clear and turns yellow, that’s also a sign it’s oxidizing and will be less effective.

Price: Factors like concentration and formulation determine a vitamin C serum’s quality, not the price tag. Prices run the gamut from $25 to more than $100.

Why L-ascorbic Acid is important for brighter skin

There are different forms of vitamin C in skin care, and L-ascorbic is just one type — but it’s one you want to look for. It’s a natural organic compound found in topical vitamin C products, such as powders, oils, and serums. It’s helpful for improving

• fine lines
• wrinkles
• hyperpigmentation
• dark spots
• acne scars

The name “L-ascorbic” refers to the chemical structure of the type of vitamin C and how it reacts to light. You may have heard of ascorbic acid — the form of vitamin C used in dietary supplements taken orally. But L-ascorbic is given its name based on how it rotates when exposed to light.

Forms of vitamin C break down into synthetic and natural versions. L-ascorbic is derived from natural sources. It’s found in fruits, vegetables, and even in human skin. The epidermis contains especially high concentrations of the organic compound.

L-ascorbic is a trustworthy source of vitamin C because it’s thoroughly researched. It’s among the most trusted active ingredients in skin care products. L-ascorbic stands out from other forms of vitamin C because it’s considered active.

Since L-ascorbic is naturally found in the skin, it’s bioavailable (aka it can be put to use immediately). The caveat is that it can be unstable, so it can oxidize before it reaches your skin.

Other forms of topical vitamin C may be more stable, but they’re considered inactive. This means they must be converted to L-ascorbic before they’re of use to the skin.

7 vitamin C serums to consider

Keep in mind that a higher percentage of L-ascorbic acid doesn’t always mean a better product. Sometimes it can be too strong for your skin, causing it to react via purging, breakouts, or itchiness. You don’t want the product to sting and itch even after you apply moisturizer.

Which vitamin C serums should you avoid?

If you have dry, dehydrated, sensitized, or sensitive skin, you may want to opt for lighter vitamin C serums that have less than 20 percent L-ascorbic acid, especially if you want to apply twice per day. If the serums you like are on the higher end, dilute it with a moisturizer with each use. Since your skin only uses 10 percent of vitamin C’s benefits, you may not need full power with each application.

What about powder to DIY my own vitamin C benefits?

Got too many skin potions already? You can add a daily pinch of vitamin C powder to an existing serum or moisturizer in your routine.

You may have seen some skin care lines touting C powders, like Philosophy’s turbo booster version, which is nearly 100 percent ascorbic acid. Or you can snag a food-grade supplement powder, like NutriBiotic, at your favorite vitamin retailer for a fraction of the cost.

Keep in mind that the combo of vitamin C with other specific ingredients, like vitamin E and ferulic acid, are what help stabilize it and allow your skin to absorb it.

So, playing chemist in your bathroom with your own array of products may not produce the same results as buying a pre-crafted serum. However, if you’re a diehard DIY-er, you can use a powder to make your own affordable and serum with all the necessary ingredients.

Whatever brand or form you buy, the bottom line is that vitamin C is one of the best tried-and-true ingredients for your skin with lots of research to back it up. You don’t need a fancy (read pricey) version to reap vitamin C’s skin-saving rewards.

How to use vitamin C serum

Vitamin C can react when paired with certain ingredients, and some forms of the antioxidant can be unstable. To get the most out of your vitamin C serum, here’s how to use it the right way.

1. Wash your face: Always start with clean skin so your vitamin C serum doesn’t mix with impurities.
2. Use a toner or essence to balance skin’s pH: Avoid toners with other acids and exfoliants.
3. Apply vitamin C to the face, neck, and chest: Look for a vitamin C serum that also contains vitamin E and ferulic acid, which can increase the stability and effectiveness of L-ascorbic.
4. Moisturize to form a protective seal around skin: Avoid creams with retinol.
5. Apply sunscreen. Vitamin C serums may increase skin’s sensitivity to sunlight.

Frequently asked questions

Is L-ascorbic acid the same as vitamin C?

L-ascorbic acid is a form of vitamin C. It’s naturally derived and found in human skin. Though it’s unstable, it’s an active form of vitamin C, so it’s bioavailable and ready for immediate use.

Are there any side effects of using Vitamin C serums?

High concentration vitamin C serums can cause irritation. Vitamin C can cause reactions when mixed with certain active ingredients, such as retinol and other acids. It can also increase photosensitivity or sensitivity to sunlight, so always apply sunscreen after using a vitamin C serum.

Should I use vitamin C serum in the morning or at night?

You can use vitamin C serum at any time of the day. It’s common to use vitamin C in the morning and retinol or exfoliants at night since they shouldn’t be mixed in the same routine. If you go this route, just make sure to use SPF when using vitamin C during the day.

Should I use vitamin C serum before or after moisturizer?

Apply your vitamin C serum before your moisturizer, facial oil, and sunscreen (but you can use a face wash and toner before your vitamin C serum).

The order of your skin care products depends on the molecule size. A vitamin C serum has smaller molecules than a moisturizer, so it should be used first. A moisturizer can then seal in the vitamin C serum.

Takeaway

Most people can benefit from using a vitamin C serum in their skin care routine. Vitamin C, especially L-ascorbic, is a highly researched active ingredient that has been shown to possess antioxidant properties. Though it’s unstable, it’s bioavailable and therefore highly regarded in the cosmetic industry.

Using a vitamin C serum has many benefits. The antioxidant fends off free radicals from environmental stressors like pollution, sunlight, and harsh weather conditions. Apply a vitamin C serum to boost skin brightness — just pair with vitamin E, ferulic acid, and SPF for best results.

Jennifer Chesak is a medical journalist for several national publications, a writing instructor, and a freelance book editor. She earned her Master of Science in journalism from Northwestern’s Medill. She’s also the managing editor for the literary magazine, Shift. Jennifer lives in Nashville but hails from North Dakota, and when she’s not writing or sticking her nose in a book, she’s usually running trails or futzing with her garden. Follow her on Instagram or Twitter.