Is benzoyl peroxide a treatment for folliculitis?

Folliculitis is an inflammation of the hair follicle. It presents itself as vesicles, pustules or papulo-pustular lesions of 1 mm in diameter in acute cases. It is contagious and can cause itching. Two types of folliculitis can exist: the infectious and the non-infectious . The infectious cause is often bacterial (such as Staphylococcus or Pseudomonas ), viral or due to fungi. Non-infectious folliculitis is caused by friction or follows ingrown hairs, due to poor hair removal or shaving techniques, or the use of certain products. Hyperkeratinisation of the hair follicles can also play a role in the onset of folliculitis. Indeed, an excess production of keratin in the hair follicle can induce a thickening of the horny layer, which is the origin of the folliculitis spots.

The benzoyl peroxide is a product found over-the-counter or on prescription at different concentrations: 2%, 5% or 10%. Its antibacterial, anti-inflammatory, keratolytic and sebostatic properties make it a widely recognised active ingredient for its effectiveness in reducing acne. The benzoyl peroxide could also be a solution against folliculitis. Indeed, some products based on benzoyl peroxide are prescribed for the treatment of folliculitis. As it is known for its antibacterial and keratolytic properties, it could reduce the two main causes of inflammation: infection by Staphylococcus aureus or by other agents such as Pseudomonas, and the hyperkeratinisation of the hair follicle.

• Reduction of hyperkeratinisation through the use of benzoyl peroxide.

  The keratolytic action of benzoyl peroxide works by loosening the bonds between the cells of the stratum corneum, thereby facilitating the removal of dead skin cells and reducing follicular obstruction. A study on 6 patients published in the journal Skin Pharmacology and Physiology revealed that the use of 2% benzoyl peroxide has a more effective keratolytic action than some products known for this property, such as the salicylic acid and retinoic acid. Indeed, after 3 hours, benzoyl peroxide was significantly more effective at weakening the bonds between the dead cells of the stratum corneum than the other products mentioned. After 6 hours, all three treatments were equally effective. However, the data obtained are not really significant, as the study was conducted on a very small number of patients.

• Regulation of bacterial populations by benzoyl peroxide.

  Although benzoyl peroxide is known for its inhibitory action against Cutibacterium acnes, the bacteria responsible for the onset of acne, it may also act on the bacteria involved in infectious folliculitis, such as Staphylococcus aureus. When applied to the skin, benzoyl peroxide splits and forms free radicals, known as reactive oxygen species, which directly act on cellular structures, such as the proteins of bacteria, by oxidising them. This disrupts their survival and function. These species also damage bacterial DNA, thus reducing the bacteria's ability to reproduce.

  A study aimed to assess the antibacterial effectiveness of benzoyl peroxide on five species of bacteria, including Staphylococcus aureus and Pseudomonas aeruginosa. The different strains were incubated at various times, depending on their type, with varying concentrations of benzoyl peroxide (0.25; 0.5; 1 and 2 mmol/L). The results show a significant reduction in the number of colonies of Staphylococcus aureus (CFU), particularly at the highest concentrations. Conversely, the number of Pseudomonas aeruginosa colonies (CFU) remained stable, even at high concentrations. In conclusion, this study indicates that benzoyl peroxide exerts a notable antibacterial activity on Gram-positive bacteria, but it is much less effective, or almost ineffective, against Gram-negative bacteria.

Despite these encouraging results, it would be interesting for studies on the direct effects of benzoyl peroxide on folliculitis to be conducted.

• HOLLAND K. T. & al. The impact of benzoyl peroxide on skin micro-organisms in vitro. National Centre for Biotechnology Information (1983).

• SABAT SANTANDREU M. & al. Folliculitis: Identification and Treatment. American Journal of Clinical Dermatology (2004).

• MAIBACH H.I. & al. 'Keratolytic' Properties of Benzoyl Peroxide and Retinoic Acid Resemble Salicylic Acid in Humans. Skin Pharmacology and Physiology (2006).

• REHMUS W.E. & al. Folliculitis. The MSD Manual (2023).