Vitamin C: The Antioxidant Powerhouse

First Posted on August 2, 2023 in:anti-agingantioxidantdecoding activeshyperpigmentationscience deep divevitamin c
Vitamin C serums is probably one of the most popular products with countless new launches every year. Their lasting popularity make a lot of sense! Simply put, Vitamin C (specifically ascorbic acid) is one of the most validated actives in the skincare world for its clinical benefits. It has been proven to prevent free radical damage, brighten hyperpigmentation, and even boost collagen production. But given vitamin C’s popularity, it’s only gotten MORE difficult to choose the best vitamin C serum for your skin with the constant sea of new launches every season.

So let’s take a closer look at all the clinically tested skin benefits of vitamin C, why a good vitamin C formula is hard to come by, who should or shouldn’t use vitamin C, and when to incorporate this multifunctional powerhouse into your routine.

Ascorbic acid vs. other vitamin C derivatives

To start, one of the most important things for us to get out of the way is that not all vitamin C’s are created equal. In fact, vitamin C is actually a whole category of ingredients. However, almost all of the proven benefits of topical vitamin C you hear of actually comes from clinical studies done on specifically L-ascorbic acid (L-AA). This is why we’d consider ascorbic acid to be the true gold standard of the vitamin C serum landscape. We’ll focus the rest of this post on all things ascorbic acid, but if you’re curious about other forms of vitamin C, head on over to our dedicated blog post on shopping for vitamin C derivatives here.

Topical Vitamin C: a proven antioxidant

how antioxidants save your skin from free radical damage

First and foremost, scorbic acid is a proven, topical antioxidant. Skin is exposed to the elements daily. External aggressors such as UVA, UVB, and pollution can create excess free radicals in skin. Free radicals are hyper reactive molecules that go on a rampage attacking anything in sight. Because of its unpaired electron, it desperately wants to pair up, making them highly reactive and creating oxidative stress. This leads to the disruption of your cells, mitochondria, and even your DNA. The accumulation of this daily damage leads to premature photoaging and comes in the forms of dull uneven skintone, dark spots, wrinkles, and sagging skin. 

Enter antioxidants like ascorbic acid to save the day! Antioxidants work by “quenching” the free radicals, essentially sacrificing itself to spare your precious skin cells. This is why continued, consistent inclusion of vitamin C serums in your routine is one of the key steps to your long-term age-prevention strategy. 

But aren’t there a lot of other good antioxidants out there?

Now, it feels like there’s a gazillion different antioxidants in the skincare world. Just about every fruit, flower, and tree bark extract gets touted as a “rich-in antioxidant”. So what makes vitamin C special in the antioxidant arena? The reality is, many antioxidants are tested in a test tube or petri dish first. Many ingredients will be tested via this method and immediately gets a “good enough!” stamp of approval to be put into bottles on shelves. But the reality is, having test tube antioxidant data doesn’t necessarily help us understand how it would perform on skin, especially in the form of a topical serum. Vitamin C ascorbic acid is one of the few antioxidants out there that has actually been tested and proven to work in the form of a topical serum. 

Ascorbic Acid can effectively brighten & fight hyperpigmentation

Being an effective antioxidant isn’t ascorbic acid’s only skin benefit! Uneven pigmentation of any type (melasma, post-inflammatory hyperpigmentation, age spots, post acne marks, etc) can be one of the most persistent, frustrating skin concerns to deal with. Even so, ascorbic acid has been clinically tested to effectively brighten skin at as low as 5% in a skin serum. In fact, there was a small study done on a group of 16 patients with melasma for 16 weeks. The participants used 5% ascorbic acid serum on one side, and a 4% hydroquinone cream on the other side of face. By the end of study, both sides showed improvement. Even though the hydroquinone-treated side showed significantly more improvement, it also comes with a lot more irritation.

In a separate study, a much higher concentration 25% ascorbic acid serum was evaluated on 40 participants with melasma for twice daily usage over 16 weeks. All participants showed significant improvement by the end of the study.

Ascorbic Acid can boost collagen production

Last! But definitely not least, ascorbic acid has also been proven to boost collagen production.

*Fun fact: You wouldn’t (also shouldn’t) hear about collagen boosting claims in actual skincare because it would be considered a drug claim.

Scientists have known since the 80s through in vitro testing on skin cells that the presence of ascorbic acid seems to boost collagen production. So in many clinical studies, study participants see active improvements in fine lines and wrinkles in addition to the skin brightening benefits.

In a French study done in the early 2000s, 20 participants applied a 5% vitamin C cream compared to a placebo over 6 months (an impressively long study in the skincare realm!). By the end of the study, the vitamin C treated side of face had significantly less fine lines, wrinkles, and skin tissue was more dense. Skin biopsies also revealed that skin collagen appeared to be more “structured” in the vitamin C treated side. Very niceee…

How do I choose the best vitamin C serum for my skin?

Convinced? Ready to add ascorbic acid to your skincare routine for the long haul? Like all powerhouse actives, there's always a catch. Ascorbic acid is infamously unstable in water, and can be a pain in the butt to formulate. Trust us, we know. To get the most out of your vitamin C serum, you must choose one that’s formulated correctly so that the formula remains stable long enough for you to get all the benefits out of it. There are 3 main forms of vitamin C products you can choose from: classic water-based serum, anhydrous suspension, and powder vitamin C. Each of these have their own sets of pros and cons.

    Water-based vitamin C serums

    This is THE classic vitamin C formula that has been patented and popularized by Skinceutical’s CE Ferulic. This format should be at a pH of lower than 3.5 with supporting antioxidants like vitamin E and ferulic acid to ensure vitamin C stability. That said, you’ll still slowly get that waft of hot dog and watch your formula gradually turn amber with this form. Since CE Ferulic’s patent expired, there’s a slew of dupes to choose from on the market. We tested a handful of the market favorites! Head on over to our dedicated blog post to see which one performed the best.

    Anhydrous vitamin C suspension serums

    Water is THE main culprit behind vitamin C degradation. One way to prevent this degradation is to simply formulate it into anhydrous (waterless) formulas. A few classic examples of these type of formulas are: Kiehl’s Powerful Strength Line Reducing Serum,  Beautystat’s Universal C Skin Refiner Brightening Vitamin C Serum, and the Ordinary Vitamin C Suspension. We highly recommend patch testing this type of vitamin C. The high solvent load can be irritating to some skin types and some formulas may be too gritty to apply or work well on skin.

    Vitamin C powders

    There are a few vitamin C powders on the market such as Philosophy’s Turbo Boost and the Ordinary vitamin C powder . This is THE most stable way to get your vitamin C. But sadly, the dosing can get pretty confusing and it definitely leaves a suspicious mess in your bathroom.

    Water-based serums is still probably your best bet if you’re entering this realm for the first time. You’ll be able to select your Vitamin C concentration (5-20%) and it ultimately is the most familiar method of application to reap those benefits. Just stay consistent, store it correctly, and be diligent in going through it if the shelf life gives you slight anxiety. 

    Key Takeaways and Routine FAQ

          Where does a vitamin C serum go in my skincare routine?

                We recommend using vitamin C serum in your morning routine as one of your first steps. Generally speaking, vitamin C should be used before your moisturizer and sunscreen.

                      Should I use vitamin C in the AM and PM?

                            You can but it’s not necessary. In research, ascorbic acid was used once a day for its antioxidant properties. For tackling stubborn pigmentation concerns, the serum was used twice a day. It’s really up to you and what fits your routine best.

                                Can you use a vitamin C serum at any age?

                                    Yes! Whether you’re interested in age prevention or tackling skin concerns, vitamin C is great for even teenage to mature skin.

                                        I have sensitive skin, can I use vitamin C?

                                            Consider starting with a lower concentration, water-based 5% ascorbic acid serum to start. Also, patch testing saves lives!

                                                Are there any side effects to vitamin C?

                                                    Everyone’s skin is unique, and ascorbic acid serums might not be for everyone. If your skin doesn’t agree with vitamin C, it might get red, irritated, or even break out. If that is the case, checkout vitamin C derivatives or non-vitamin C antioxidant options.


                                                    Vitamin C serums are great for actively tackling hyperpigmentation AND long term age prevention. It’s important to make sure you’re looking for serums with specifically, ascorbic acid, to reap all of the great Vitamin C benefits. Because Vitamin C is not stable in water, it typically comes in three types of products: water-based, anhydrous, and powders. There are pros and cons to each type and the best product is one that you can consistently use in your routine.

                                                    Does ascorbic acid not quite work for your skin? Curious about vitamin C derivatives or other antioxidants? Check out our dedicated blog posts!


                                                    Pinnell, S. R., Yang, H., Omar, M., Riviere, N. M., Debuys, H. V., Walker, L. C., ... & Levine, M. (2001). Topical L‐ascorbic acid: percutaneous absorption studies. Dermatologic surgery, 27(2), 137-142.

                                                    Espinal‐Perez, L. E., Moncada, B., & Castanedo‐Cazares, J. P. (2004). A double‐blind randomized trial of 5% ascorbic acid vs. 4% hydroquinone in melasma. International journal of dermatology, 43(8), 604-607.

                                                    Hwang, S. W., Oh, D. J., Lee, D., Kim, J. W., & Park, S. W. (2009). Clinical efficacy of 25% L-ascorbic acid (C'ensil) in the treatment of melasma. Journal of cutaneous medicine and surgery, 13(2), 74-81.

                                                    Murad, S., Grove, D., Lindberg, K. A., Reynolds, G., Sivarajah, A., & Pinnell, S. (1981). Regulation of collagen synthesis by ascorbic acid. Proceedings of the National Academy of Sciences, 78(5), 2879-2882.

                                                    Humbert, P. G., Haftek, M., Creidi, P., Lapière, C., Nusgens, B., Richard, A., ... & Zahouani, H. (2003). Topical ascorbic acid on photoaged skin. Clinical, topographical and ultrastructural evaluation: double‐blind study vs. placebo. Experimental dermatology, 12(3), 237-244.


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