Hypochlorous Acid

Hypochlorous acid is primarily used as an antimicrobial/anti-inflammatory in leave-on sprays or wound/eczema-adjacent care, typically at very low concentrations (~0.005–0.02%) and near-skin pH, where clinical use is generally well tolerated. However, as an oxidizing biocide it can still sting on compromised skin and can irritate eyes or reactive faces (especially if the formulation has higher free available chlorine or is off-pH), so it is best classified as very gentle rather than inert. Safety Notes: In consumer leave-on hypochlorous acid facial/body sprays and mists, the lowest commercially observed levels are around ~0.005% (≈50 ppm) to provide mild antimicrobial/soothing benefits with good tolerability, while the most common market level clusters near ~0.01% (≈100 ppm). High-strength OTC specialty sprays marketed for more intensive antimicrobial/deodorizing use typically top out around ~0.02–0.03% (≈200–300 ppm) because higher HOCl levels are harder to stabilize (pH/ORP constraints) and are more likely to be irritating; products above this are generally positioned as disinfectants or are not typical cosmetic leave-ons.