The Science of Hypochlorous Acid (HOCI) in Skin Care

Hypochlorous acid (HOCl) is a molecule your body already makes. As a byproduct of the immune system's response to infection, this ingredient is effective enough to be used in clinical wound care, yet gentle enough for daily use on sensitive skin. Learn more about what hypochlorous acid is here, plus how it can benefit the skin, its safety profile, and who it’s best for.

Hypochlorous acid (HOCl) is a weak acid that is naturally produced by neutrophils – a type of white blood cell – when the immune system needs to destroy pathogens after they are engulfed by phagocytic cells. Thus, HOCl acts as a direct antimicrobial agent, toxic to the cell walls of bacteria and other microorganisms (3).

HOCl is chemically related to sodium hypochlorite, the active compound in household bleach. The key difference between them is pH. Hypochlorous acid has an acidic to near-neutral pH (roughly 3.5 to 5.5), making it gentler than sodium hypochlorite, which has a higher, more alkaline pH level (3). Stabilizing Hypochlorous acid at the correct pH has been a significant formulation challenge, but modern electrolyzed water technology – processing pure water and sodium chloride through an electrochemical reaction – has made it possible to produce stable, hypochlorous acid solutions with shelf lives of up to two years (3).

• Antimicrobial action without resistance – hypochlorous acid kills acne-causing bacteria through oxidative cell wall damage rather than receptor binding, so bacteria cannot develop resistance to it the way they do to conventional antibiotics (3).

• Acne reduction – A double-blind, placebo-controlled randomized trial found stabilized hypochlorous acid comparable in efficacy to benzoyl peroxide for mild to moderate inflammatory acne (4).

• Anti-inflammatory effects – Laboratory studies show that hypochlorous acid reduces the activity of several pro-inflammatory mediators, including histamine, leukotriene B4 (LTB4), IL-6, and IL-2, and inhibits IgE-induced mast cell degranulation (3).

• Atopic dermatitis and itch support – Topical hypochlorous acid reduces Staphylococcus aureus on the skin, which is a key cause of inflammation and itch in eczema-prone patients (3).

• Barrier-friendly for dry and rosacea-prone skin – Hypochlorous acid does not disrupt sebum production or strip the moisture barrier, making it appropriate for skin types that can’t tolerate other acne treatments.

• Wound healing and post-procedure support – Hypochlorous acid promotes keratinocyte and fibroblast migration and can help to reduce the appearance of hypertrophic scars and keloids after procedures (3).

While the Environmental Working Group (EWG) flags hypochlorous acid as unacceptable for its EWG Verified products, much of the EWG's reference data for HOCl draws from studies involving inhalation exposure to chlorine-related compounds and industrial-grade hypochlorite, not the low-concentration, stabilized, pH-neutral topical formulations used in skin care products. EWG lists this ingredient as having low cancer and reproductive harm risks. 

The Cosmetic Ingredient Review (CIR) has not published a formal safety assessment specifically for hypochlorous acid as a cosmetic ingredient. 

Skin care products with hypochlorous acid are often formulated as lightweight mists or sprays, since the stabilized HOCl solution requires minimal additional ingredients to remain effective.

Hypochlorous acid provides direct antimicrobial action without antibiotic receptor binding, making it a gentle option for acne-prone skin. It does not promote bacterial resistance or strip away sebum, and it is generally well-tolerated by sensitive and inflamed skin types. The research base is still growing, particularly for rosacea-specific applications, but the anti-inflammatory and barrier-supportive properties of stabilized topical hypochlorous acid are supported by clinical research.

For those managing acne, redness, or compromised skin who need something that works while remaining gentle on the skin, hypochlorous acid products may be a good fit. Take the Baumann Skin Type Quiz to get personalized product recommendations based on your specific skin type.

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1. Sally R, Reider E, Acne Type 1 Sensitive Skin in Ch.16 of Baumann's Cosmetic Dermatology Ed 3. (McGraw Hill 2022)
2. Baumann, L. Antiacne Ingredients Ch.75 Cosmeceuticals and cosmetic Ingredients (McGraw Hill 2015)
3. Del Rosso JQ, Bhatia N. Status report on topical hypochlorous acid: clinical relevance of specific formulations, potential modes of action, and study outcomes. J Clin Aesthet Dermatol. 2018;11(11):36–39.
4. Tirado-Sánchez A, Ponce-Olivera RM. Efficacy and tolerance of superoxidized solution in the treatment of mild to moderate inflammatory acne: a double-blind placebo-controlled, parallel-group, randomized, clinical trial. J Dermatol Treat. 2009;20(5):289–292. DOI: 10.1080/09546630902973995.