Hypochlorous Acid for Disease Transmission Prevention
Hypochlorous acid (HOCl) is highly effective for preventing disease transmission through surface disinfection and environmental decontamination, but its use should be limited to surfaces and environmental applications rather than direct human application for disease prevention.
Evidence for Surface and Environmental Disinfection
Antimicrobial Efficacy
HOCl demonstrates broad-spectrum antimicrobial activity against bacteria, viruses, and other pathogens when applied to surfaces and in environmental settings 1, 2.
Liquid HOCl at concentrations of 20-200 ppm achieves ≥99.9% (≥3 log10) reduction in viral infectivity on both porous (ceramic tile) and nonporous (stainless steel) surfaces within 10 minutes of exposure 3.
HOCl effectively inactivates human norovirus, murine norovirus, and coliphage MS2 on contaminated surfaces, making it suitable for controlling virus spread via fomites 3.
Aerosolized HOCl at 300 ppm demonstrates bactericidal effectiveness of 96-99.9% on flat and porous surfaces, though only 69% on semi-porous surfaces 4.
Application Methods
HOCl can be applied as a liquid disinfectant or as an aerosolized fog for large-space decontamination 3, 4.
When fogged in confined spaces, HOCl reduces viral infectivity and RNA titers by at least 99.9% (3 log10) regardless of carrier location and orientation 3.
For optimal aerosolized application, particle size should be less than 200 μm to increase pathogen contact, with exposure duration of at least 60 seconds at concentrations as low as 20 ppm 5.
The pH must be maintained between 3.5-5.0 to keep HOCl stable and maximize antimicrobial activity while minimizing undesirable side products 1.
Critical Limitations for Human Disease Prevention
Not a Substitute for Standard Hand Hygiene
The provided guidelines do not support HOCl as a replacement for established hand hygiene protocols using alcohol-based hand rubs or soap and water 6.
Alcohol-based hand sanitizers remain the gold standard for hand antisepsis in healthcare settings, demonstrating superior efficacy compared to antimicrobial soaps containing chlorhexidine, povidone-iodine, or triclosan 6.
For healthcare workers, alcohol-based hand rubs prevent pathogen transfer in 83% of cases compared to only 8% with plain soap and water 6.
Environmental Use in Healthcare Settings
Sodium hypochlorite (chlorine bleach) solutions containing >2 mg/L (>2 ppm) free residual chlorine are recommended for environmental decontamination in healthcare facilities, particularly for Clostridioides difficile control 6.
Hand hygiene with soap and water—not alcohol-based sanitizers—is the cornerstone for preventing C. difficile transmission, as alcohol does not kill spores 6.
For Legionella control in water systems, hyperchlorination with >2 mg/L free residual chlorine or maintaining heated water at 1-2 mg/L free residual chlorine at the tap is recommended 6.
Safety Considerations for Immunocompromised Patients
Respiratory Safety Concerns
While HOCl at 300 ppm does not affect cellular viability in 2D and 3D skin and lung models in laboratory settings 4, more investigation is needed regarding respiratory system effects when humans transition through HOCl mist or fog environments 5.
For immunocompromised patients (transplant recipients, neutropenic patients), standard infection control measures remain paramount: contact precautions, environmental cleaning with appropriate disinfectants, and strict hand hygiene protocols 6.
Appropriate Use Context
HOCl is best utilized for surface disinfection and environmental decontamination rather than as a personal protective measure for individuals 1, 2, 3.
Healthcare workers and visitors with symptomatic infections should not engage in patient care or visit immunocompromised patients unless appropriate barrier protection (masks, gloves) is established 6.
Common Pitfalls to Avoid
Do not use HOCl as a substitute for proven hand hygiene methods—alcohol-based hand rubs or soap and water remain superior for personal disease prevention 6.
Avoid assuming all chlorine-based products are equivalent—sodium hypochlorite solutions used for environmental cleaning differ in concentration and application from stabilized HOCl products 6.
Do not apply HOCl in inadequately ventilated spaces without proper safety evaluation, particularly when immunocompromised individuals are present 5.
Ensure adequate contact time (minimum 60 seconds for aerosolized applications, 10 minutes for liquid applications) to achieve effective pathogen reduction 3, 5.