Keratinocyte deviations in proliferation, adhesion and differentiation obstruct the infundibulum and the sebaceous duct, paving the way for excessive sebum secretion, bacterial overgrowth such as Propionibacterium acnes (P. acnes), and inflammatory response due to release of bacterial and cellular products, i.e. sebum and keratin. Keratolytic agents are believed to function by relaxing the cohesiveness of the stratum corneum (SC). This involves the disintegration of desmosomes and hemidesmosomes, which link keratinocytes and bind them to the extracellular matrix (ECM), respectively. Therefore, keratolytic agents modulate and correct abnormal follicular keratinization.
Benzoyl peroxide (BPO), a mainstay treatment of mild to moderate acne, has antimicrobial, anti-inflammatory and anticomedogenic effects. Its lipophilicity allows it to enter and accumulate in the lipid-rich pilosebaceous units and subcutaneous fat. Since the pathogenesis of acne begins in the pilosebaceous unit, this may explain the efficacy of BPO.
An eight-week study was conducted where 2.5% BPO was compared with 5% BPO, 10% BPO and its vehicle. BPO at 2.5% significantly decreased inflammatory lesions, i.e. papules and pustules, compared with the vehicle alone; in addition, it showed equivalent efficacy to 5% and 10% BPO while producing fewer side effects than 10% BPO. The only significant adverse effect in this study was skin peeling.
In addition to peeling, adverse effects of BPO can include dryness, burning and redness of skin, and contact allergy occurs in 1–2% of consumers. To that end, products including BPO should advise consumers on the label to avoid excessive UV radiation, which can exacerbate irritation.
Combination therapy of BPO with topical antibiotics may be more effective than BPO alone in treating mild to severe acne. Both clindamycin/BPO and erythromycin/BPO formulations have shown superior efficacy when compared with BPO or antibiotic monotherapy. Topical antibiotics aid BPO in treating acne by exerting an anti-inflammatory action as well as an antimicrobial action against P. acnes.