Is vitamin C useful for combating skin blemishes?

According to the French Society of Dermatology, there are more than 15 million people in France, including 3.3 million over the age of 15, affected by acne.

This skin condition is the primary reason for consultations with a dermatologist and can cause significant distress for the individual due to its visible appearance. The blemishes develop in the pilosebaceous follicles when the sebaceous glands secrete sebum that is too thick or in excessive quantity, blocking the openings. This hyperseborrhoea or dysseborrhoea often stems from hormonal imbalance. At the same time, accelerated cell turnover can lead to an accumulation of dead cells on the skin surface, contributing to pore blockage. In this lipid-rich environment, a bacterium present in low numbers on the skin, Cutibacterium acnes, proliferates and releases pro-inflammatory mediators. At this point they are no longer simple blackheads or whiteheads that appear on the skin, but papules or pustules, and in some cases nodules, which are inflammatory lesions.

Regarding vitamin C, in any form, to date there is no clinical study in humans demonstrating that it can target blemishes.

However, this ingredient does not appear to have sebum-regulating or keratolytic effects, both essential for addressing blemishes at their source. That said, the vitamin C may be of interest for skin prone to blemishes. Several properties of ascorbic acid – such as its anti-inflammatory, antioxidant and antibacterial effects – suggest it could play a complementary role in managing blemishes.

First, vitamin C has an anti-inflammatory action that may help reduce redness associated with inflammatory lesions. Several studies have shown that ascorbic acid can inhibit activation of NF-κB, a transcription factor linked to the innate immune response. This factor plays a central role in initiating and maintaining inflammation by stimulating the production of pro-inflammatory cytokines such as TNF-α and interleukins 1, 6 and 8. By modulating this signalling pathway, vitamin C may prevent the worsening of blemishes into inflammatory lesions and thus avoid post-inflammatory erythema, the persistent red marks that appear after inflammatory acne lesions have healed.

Another potential benefit of vitamin C in addressing blemishes: its antioxidant properties, which may allow it to protect sebum from oxidation, in particular squalene, one of its main components. When exposed to reactive oxygen species (ROS), squalene can undergo peroxidation, leading to squalene peroxide, a comedogenic, pro-inflammatory compound. Squalene peroxide stimulates keratinocyte proliferation, a process that promotes hyperkeratinisation and the buildup of dead cells on the stratum corneum. Ascorbic acid, by donating an electron, can stabilise free radicals before they oxidise squalene. It then converts to dehydroascorbic acid, stable due to its aromatic cyclic structure.

Moreover, although no study to date has demonstrated a direct effect of vitamin C on C. acnes, several studies have highlighted the antibacterial properties of this ingredient against other microorganisms. In a comparative disc diffusion test, researchers evaluated vitamin C at concentrations of 5, 10 and 20 mg/mL against seven bacterial strains and compared it with erythromycin, an antibiotic used against acne. As a reminder, the disc diffusion test involves placing a disc impregnated with the test molecule on an agar plate containing bacteria to observe whether a growth-free zone appears around the disc, indicating an antibacterial effect. The results, shown in the table below, demonstrate a broad-spectrum antibacterial activity of vitamin C. From a mechanistic perspective, vitamin C is assumed to disrupt bacterial biofilm formation, preventing microorganisms from proliferating.

Finally, a preclinical study recently investigated the potential effect of vitamin C on acne by combining it with an established topical retinoid , adapalene. Researchers used a testosterone-induced murine acne model that reproduces key features of human acne, including inflammation of the sebaceous glands. Five groups were formed: a control group receiving only testosterone injections (group 1), a group treated with unencapsulated adapalene (group 2), a group receiving encapsulated adapalene (group 3), a group treated with a gel combining encapsulated adapalene and vitamin C (group 4), and a healthy control group (group 5). Encapsulation aimed to improve stability and penetration of the active ingredients.

In fact, the gel combining encapsulated adapalene and vitamin C (group 4) proved most effective in reducing inflammation, decreasing lesion size, and restoring normal skin histological architecture. Its effects exceeded those observed with adapalene alone, whether encapsulated or not, suggesting a potential synergistic effect between the two actives. Although this study was conducted in animals and cannot be extrapolated to humans, it reinforces the idea that vitamin C, with its anti-inflammatory and antioxidant properties, could play a supportive role in managing skin prone to imperfections.

If you have acne, an appointment with a dermatologist is essential to obtain tailored treatment. Over-the-counter products can support treatment. They are sufficient for isolated or occasional blemishes.

• HONGBIN L. & al. Role of vitamin C in skin diseases. Frontiers in Physiology (2018).

• HEIMESAAT M. M. & al. Immunomodulatory and antimicrobial effects of vitamin C. European Journal of Microbiology and Immunology (2019).

• DUBEY A. & al. Development and investigation of vitamin C-enriched adapalene-loaded transfersome gel: a collegial approach for the treatment of acne vulgaris. AAPS PharmSciTech (2020).

• ZHOU B. & al. Prooxidative inhibition against NF-κB-mediated inflammation by pharmacological vitamin C. Free Radical Biology and Medicine (2022).

• WATKINS D. & al. Antioxidant and anti-tumor effects of dietary vitamins A, C, and E. Antioxidants (2023).

• MUMTAZ S. & al. Evaluation of antibacterial activity of vitamin C against human bacterial pathogens. Brazilian Journal of Biology (2023).