Can vitamin C act against brown spots?

What are the effects of vitamin C on pigmented spots?

More common than one might think, the hyperpigmentation is a skin condition due to a localized or diffuse increase in melanin, the pigment produced by melanocytes to protect the skin. This overproduction can be triggered by several factors: UV exposure, skin inflammation (such as after acne), hormonal fluctuations, aging, or certain medications. In these situations, the melanogenesis goes into overdrive: tyrosinase, the enzyme that converts tyrosine, an amino acid, into melanin, becomes more active and promotes the appearance of darker areas on the skin. Hyperpigmentation is very difficult to fade with cosmetic solutions.

Nevertheless, certain active ingredients, such as vitamin C, can target excess melanin and reduce pigmented spots.

The vitamin C interacts directly with melanogenesis mechanisms and primarily targets tyrosinase. By binding to the copper ions in tyrosinase’s active site, vitamin C diminishes its catalytic activity and therefore limits melanin production, which can gradually fade pigmented spots. Furthermore, the ability of the vitamin C to neutralize reactive oxygen species reduces UV-induced inflammation—a factor often implicated in excessive melanocyte stimulation. Altogether, these effects explain why vitamin C is an effective active ingredient for evening out skin tone and reducing brown spots.

An interesting clinical study evaluated the efficacy of a cream containing 25% stabilized vitamin C on melasma in 40 participants. This open-label trial was conducted over sixteen weeks. Pigmentation progression was monitored every four weeks using the MASI (Melasma Area and Severity Index), an index measuring melasma severity, and a mexameter, while the impact of hyperpigmentation on quality of life was also assessed using the MelasQoL (Melasma Quality-of-Life) index. After sixteen weeks of application, the results demonstrated a significant reduction in pigmentation.

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22.88%

reduction in the MASI score after 16 weeks (from 15.60 to 12.03)

7.56%

decrease in mexameter measurements after 16 weeks (from 215.01 to 198.75)

The MelasQoL scores also improved by an average of 10%, suggesting a positive effect on patients’ perception of their complexion and on their quality of life. In fact, the photos below, although in black and white, illustrate the reduction of pigmented spots thanks to vitamin C. These data confirm that this active ingredient can help reduce the intensity of melasma, especially when it is stabilized.

Avant et 16 semaines après application d'une crème à 25% de vitamine C stabilisée. — Before and 16 weeks after application of a cream containing 25% stabilized vitamin C.
Source: PARK S. W. & al. Clinical efficacy of 25% L-ascorbic acid (C'ensil) in the treatment of melasma. Journal of Cutaneous Medicine and Surgery (2009).

These findings are consistent with other studies on ascorbic acid. A study involving sixteen women with melasma evaluated over sixteen weeks the daily application of a 5% ascorbic acid cream to one side of the face and a 4% hydroquinone cream to the other, with each participant also using a daily sunscreen protection. Changes were measured by colorimetry and digital photography, supplemented by subjective evaluation. The results show that patient‐perceived improvement was more pronounced on the hydroquinone side, rated "good" or "very good" by 93% of participants, compared to the vitamin C side, where 62.5% of volunteers rated the improvement as "good" or "very good". Colorimetric measurements, however, revealed no statistical difference between the two formulations.

Avant et 16 semaines après application d'une crème à 5% de vitamine C. — Before and 16 weeks after applying a 5% vitamin C cream.
Source: CASTANEDO-CAZARED J. P. & al. A double-blind randomized trial of 5% ascorbic acid vs. 4% hydroquinone in melasma. International Journal of Dermatology (2004).

In contrast, adverse effects occurred significantly more often with hydroquinone (68.7%, i.e., 11/16) than with vitamin C (6.2%, i.e., 1/16). The authors conclude that, despite its lower subjective efficacy, vitamin C represents an interesting option in the management of melasma, particularly given its excellent tolerability profile.

Other studies have also confirmed the depigmenting properties of vitamin C, making this active ingredient a relevant solution for reducing brown spots and improving the uniformity of skin tone.

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