The truth about vitamin C serum

Tried every ‘brightening’ serum and still seeing no change? You’re not alone. Vitamin C is one of the most popular skincare ingredients in Australia, and for good reason: it’s a proven antioxidant, with some benefits for pigmentation and collagen. But despite the glowing reviews and hefty price tags, it isn’t the all-purpose solution it’s often made out to be.

What vitamin C can do

• Defend against environmental stress. It neutralises free radicals from UV, pollution and oxidative stress, which makes it a sensible addition to a morning routine. Think of it as one line of defence, not your only one, and never a replacement for sunscreen.
• Fade very mild pigmentation. It can help mild, surface-level pigmentation, but only alongside daily sunscreen.
• Support collagen production. Vitamin C plays a key role in the skin’s own collagen-making machinery, so it can be useful long-term as part of a broader routine.

What it can’t do

• Treat melasma, deep acne marks or significant pigmentation. It simply isn’t strong enough for hormonal pigmentation or melasma, which usually need medical assessment and care.
• Suit every skin. The effective form is acidic and can irritate, especially sensitive or acne-prone skin, or skin already using exfoliating acids or retinoids. Irritation can lead to breakouts and even darker pigmentation.
• Replace sunscreen. Vitamin C doesn’t block UV. You still need a broad-spectrum SPF every day.

RelatedMelasma vs hyperpigmentation: how to tell the difference

L-ascorbic acid vs derivatives

When we talk about vitamin C, we mean L-ascorbic acid, the only form that’s biologically active in skin. It’s water-soluble, so getting it through the skin’s oily barrier means making the formula acidic. It’s also unstable once mixed with water, so it needs careful formulation with other antioxidants (hence the famous ‘hot dog water’ smell of some serums) and packaging that protects it from light and air.

To get around these problems, the industry developed vitamin C ‘derivatives’, with tongue-twisting names such as 3-O-ethyl ascorbic acid and tetrahexyldecyl ascorbate. Scientifically, they aren’t really vitamin C, and the evidence that they work is mixed at best. Many are sold as ‘gentle’ alternatives, and many are still expensive.

Vitamin C and melasma

Well-formulated L-ascorbic acid can reduce pigment production a little, by binding the copper that tyrosinase, the key pigment-making enzyme, needs to work. In theory, that should help. In practice, the evidence for melasma is thin.

Only two small studies have tested vitamin C alone for melasma, both using 5% L-ascorbic acid:

• In the first, 29 people had vitamin C on one side of the face and water on the other for 12 weeks. An instrument detected a little less pigment on the vitamin C side, but the participants couldn’t see any difference between the two sides.
• The second, a poorly designed study of 16 people, compared vitamin C with a prescription fading cream. 93% rated their results ‘good to excellent’ on the prescription side, compared with 63% on the vitamin C side.

Formal evidence grading systems give vitamin C the lowest grade (D) for melasma. It can play a supporting role as an antioxidant once pigmentation is under control, but it isn’t a treatment.

Why your serum might not be working

• It’s a derivative, not L-ascorbic acid, and has little evidence behind it.
• The strength or pH is wrong. The evidence supports at least 15% L-ascorbic acid at around pH 3.2.
• It’s irritating your skin, which can cancel out any benefit.
• The problem needs more than skincare. Melasma and significant pigmentation usually do.
• You’re combining it with retinol or exfoliants without guidance, which can cause irritation, breakouts or darker pigmentation.

How to use it

Apply a few drops to clean skin each morning, before sunscreen. If you use prescription skincare, check with your doctor or nurse before adding vitamin C, to avoid irritation that can trigger breakouts, perioral dermatitis or pigmentation. And be patient: results come with consistent use and proper sunscreen, not overnight.

References

1. Pullar JM, Carr AC, Vissers MCM. The roles of vitamin C in skin health. Nutrients. 2017;9(8):866.
2. Enescu CD, Bedford LM, Potts G, Fahs F. A review of topical vitamin C derivatives and their efficacy. J Cosmet Dermatol. 2022;21(6):2349-59.
3. Sanabria B, Berger LE, Mohd H, et al. Clinical efficacy of topical vitamin C on the appearance of wrinkles: a systematic literature review. J Drugs Dermatol. 2023;22(9):898-904.
4. Huh CH, Seo KI, Park JY, et al. A randomized, double-blind, placebo-controlled trial of vitamin C iontophoresis in melasma. Dermatology. 2003;206(4):316-20.
5. Espinal-Perez LE, Moncada B, Castanedo-Cazares JP. A double-blind randomized trial of 5% ascorbic acid vs. 4% hydroquinone in melasma. Int J Dermatol. 2004;43(8):604-7.
6. Sarma N, Chakraborty S, Poojary SA, et al. Evidence-based review, grade of recommendation, and suggested treatment recommendations for melasma. Indian Dermatol Online J. 2017;8(6):406-42.
7. McKesey J, Tovar-Garza A, Pandya AG. Melasma treatment: an evidence-based review. Am J Clin Dermatol. 2020;21(2):173-225.
8. Murray JC, Burch JA, Streilein RD, et al. A topical antioxidant solution containing vitamins C and E stabilized by ferulic acid provides protection for human skin against damage caused by ultraviolet irradiation. J Am Acad Dermatol. 2008;59(3):418-25.
9. Frei B, England L, Ames BN. Ascorbate is an outstanding antioxidant in human blood plasma. Proc Natl Acad Sci U S A. 1989;86(16):6377-81.
10. Ngan V. Topical vitamin C. DermNet. Reviewed 2023.

This article is general information only. It isn’t a substitute for personal medical advice, so speak with a health professional about your own skin.