HX23 Battlefield to bathwater: the evolution of sodium hypochlorite in dermatology

Abstract

Sodium hypochlorite, commonly known as bleach, was first isolated in 1789 by Claude Louis Berthollet in Paris following recognition of its bleaching and disinfectant properties. Initial widespread use was industrial, notably in textile bleaching and water purification preceding later medical applications. Hypochlorous acid, derived from sodium hypochlorite in aqueous solution, is produced endogenously by neutrophils as part of the innate immune response, illustrating an intriguing link between chemical antisepsis and dermatological host defence. In 1847, Ignaz Semmelweis, the ‘saviour of mothers’, demonstrated that handwashing with chlorinated solutions markedly reduced puerperal sepsis, underscoring the importance of antisepsis at the skin interface. This principle was further developed during World War I, when Henry Drysdale Dakin and Alexis Carrel introduced Dakin’s solution – a buffered 0.4–0.5% sodium hypochlorite preparation for treatment of infected and gangrenous wounds. This represented an early effort to balance antimicrobial efficacy with preservation of tissue integrity. Although sodium hypochlorite is corrosive and may cause skin irritation at higher concentrations, controlled dilution enabled safe application. In the early 2000s, dilute bleach baths (approximately 0.005% sodium hypochlorite) gained popularity as an adjunctive therapy for moderate-to-severe atopic dermatitis. Huang et al. demonstrated in a 2009 Pediatrics study that a targeted antistaphylococcal regimen including dilute bleach baths led to significant improvements in eczema disease severity. Bleach baths are endorsed in guidelines within the American Academy of Dermatology and EuroGuiDerm, and are highlighted in the BAD’s eczema guidance, alongside trust-dependent local protocols. While sodium hypochlorite was initially introduced to reduce the burden of Staphylococcus aureus, emerging evidence suggests that clinical benefit is mediated predominantly through potential anti-inflammatory effects and modulation of epidermal barrier function. The continued use of sodium hypochlorite represents a rare continuity between historical practice and modern therapeutics, demonstrating how an 18th-century antiseptic remains relevant in contemporary dermatological care.