Benzoyl Peroxide versus Salicylic Acid: which one to choose for acne?

Acne is a common and often troublesome inflammatory disease, affecting approximately 80% of the global population, particularly teenagers. It is characterised by an excess of sebum, hyperkeratinisation, and colonisation by the bacterium Cutibacterium acnes, leading to inflammation. To alleviate these symptoms, various techniques such as laser and micropeeling are available, but less invasive treatments like topical care may be more suited to individual needs. The benzoyl peroxide and salicylic acid are among the active ingredients recognised for their effectiveness against acne.

• Salicylic acid, a liposoluble active ingredient with sebostatic and anti-inflammatory properties.

  The salicylic acid, a beta-hydroxy acid (BHA) often used for mild forms of acne, works in several ways to reduce symptoms. Whether it's over-the-counter or prescription, salicylic acid is used at concentrations below 2% according to European cosmetic regulations. The salicylic acid has keratolytic and antibacterial properties and soothes irritations and redness. Indeed, it intervenes in the reaction cascade leading to the synthesis of arachidonic acid and inhibits the synthesis of prostaglandins E2, molecules responsible for inflammatory and painful effects.

  However, its primary function is sebostatic. In a study published in the Journal of Dermatology, researchers investigated its effect on SEB-1 sebocytes, cells specialised in sebum production, and found that salicylic acid inhibits lipid production by activating AMPK enzymes and SREBP-1 proteins, which regulate sebum.

  Furthermore, this liposoluble active ingredient stands out for its interesting properties in the fight against blackheads, which form due to a blockage of hair follicles. Thanks to its solubility in lipids, salicylic acid can effectively penetrate the intercellular spaces of the epidermis and reach the clogged pores to eliminate accumulated impurities. According to a study evaluating the effectiveness of an exfoliant containing 30% salicylic acid, the average number of facial lesions decreased from 68.2 to 39 over 12 weeks, with non-inflammatory lesions reducing from 43 to 28 and inflammatory lesions from 25 to 11. These results suggest a notable effect on acne, but must be interpreted with caution due to the small sample size (n = 35), limiting the scope of the conclusions.

• Benzoyl peroxide is used for its antibacterial, keratolytic, and anti-inflammatory action.

  The benzoyl peroxide is an active ingredient recommended for inflammatory acne forms. It is available in various concentrations, including 2.5%, 5%, and 10%, depending on the severity of the acne. Its primary action is antibacterial. It works by oxidising the proteins of bacteria Cutibacterium acnes, which are responsible for the inflammation. According to a study published in the Journal of the National Center for Biotechnology Information, daily application of 10% benzoyl peroxide for two weeks reduced the amount of Cutibacterium acnes in hair follicles by 98%. However, these findings should be interpreted with caution as the number of participants in this test was not disclosed.

  Furthermore, the carbon dioxide that forms through the dissociation of benzoyl peroxide once it is applied to the skin promotes cellular renewal by stimulating the detachment of dead cells, which allows for the reduction of hyperkeratinisation. Indeed, it slightly acidifies the environment and enhances the metabolic activity of the cells. The anti-inflammatory property of benzoyl peroxide is, on the other hand, indirect as it is the reduction of the bacterial load that induces a decrease in inflammatory reactions.

Salicylic acid and benzoyl peroxide combined for optimal effectiveness?

The combination of salicylic acid and benzoyl peroxide could enhance the effectiveness of these ingredients against acne. In a 12-week study conducted on 50 patients suffering from mild to moderate acne, the efficacy and tolerance of a treatment combining 3% salicylic acid, 1% clindamycin and 5% benzoyl peroxide was evaluated. The addition of salicylic acid resulted in significantly better and faster results in terms of reducing acne lesions, with a decrease of 94.3% of acne for the combined treatment versus 79.2% for clindamycin and benzoyl peroxide alone. Patients observed a reduction in lesions as early as week 2 with the formula including salicylic acid, while improvement with the treatment without salicylic acid began from week 8. However, the combination was less well tolerated, with a higher frequency of certain adverse reactions.

Although benzoyl peroxide and salicylic acid are effective against acne, they nonetheless have undesirable effects. According to a safety review conducted by Health Canada to assess the potential risk of hypersensitivity, it was noted that skin irritation and dryness are the most frequently encountered side effects following the use of benzoyl peroxide or salicylic acid. Signs of irritation that may appear include redness, burning, excessive peeling, and slight swelling.

Furthermore, benzoyl peroxide is known to be photosensitising, increasing the skin's sensitivity to UV rays, but also for discolouring hair and fabrics due to its strong oxidising power. Therefore, it is advisable to use it in the evening, avoiding contact with hair and clothing, and to apply sun protection the following day.

To minimise the risk of reactions, it is crucial to adhere to the quantities and usage frequencies indicated on the user instructions of products containing benzoyl peroxide or salicylic acid.

Based on the data collected regarding the two products, here is a summary of which to choose. Thanks to its liposoluble properties, salicylic acid penetrates deeply into the pores and effectively targets non-inflammatory acne as well as comedones. This active ingredient is suitable for patients with mild to moderate acne with comedones and blackheads. Benzoyl peroxide, on the other hand, is particularly suited for forms of moderate to severe acne, especially inflammatory acne, due to its powerful antibacterial action.

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• DRÉNO.B. Données récentes sur l’épidémiologie de l’acné. Annales de Dermatologie et de Vénéréologie (2010).

• GÜNES A. T. & al. Efficacy of the addition of salicylic acid to clindamycin and benzoyl peroxide combination for acne vulgaris. Journal of Dermatology (2012).

• VIDAL. Substance active Peroxyde de benzoyle (2013).

• SANTE CANADA. Résumé de l'examen de l'innocuité - Produits topiques contre l'acné en vente libre contenant du PEROXYDE DE BENZOYLE ou de l'ACIDE SALICYLIQUE - Évaluation du risque potentiel de réactions allergiques graves (réactions d'hypersensibilité graves) (2015).

• JIANG. X. & al. Salicylic acid treats acne vulgaris by suppressing AMPK/SREBP1 pathway in sebocytes. Experimental Dermatology (2019).