HOCL as an antimicrobial

Topical antimicrobials are frequently used in conjunction with treatment and surgery to prevent and reduce the likelihood of infection. Hypochlorous acid (HOCl) is naturally occurring and its benefits has been well documented. The use and safety of HOCl as an antimicrobial in healthcare settings is supported by available evidence.

In the human body, cells produce hypochlorous acid – which helps destroy bacteria – thus making HOCl a naturally occurring chemical. Hypochlorous acid (HOCl) is a weak acid consisting of reactive oxidizing molecules that include hypochlorous acid and peroxide. This evolutionary response of white blood cells has allowed them to combine hydrogen peroxide and an enzyme known as myeloperoxidase to produce HOCl which safely and effectively eradicates any known pathogen in nature.  HOCl has enabled our biology (i) to eradicate every pathogen by dissociating into different oxidative molecules each with a distinct mode of action and capability to eradicate pathogens (ii) while remaining safe to mammalian cells through the entire biological process and (iii) not promoting the emergence of newly resistant bacteria.

HOCl is a potent antimicrobial capable of eradicating bacteria including antibiotic-resistant strains, viruses, fungi, and spores. For more than 25 years the technology has been used worldwide primarily for the mechanical cleansing and debridement of wounds. “Chlorine-containing biocides are widely used for the decontamination of surfaces, usually in the form of hypochlorite (ClO−), being inexpensive to produce and having proven antimicrobial activity”. Applications of aqueous solutions containing approximately 30-2500 ppm (.003% to 0.25%) HOCl are in a variety of areas including (but not limited to) wound care4, as antimicrobial agents5, as anti-allergen agents6, dental care7 and there are also significant applications in water treatments8, food sanitization9, and hard surface disinfection10, oil drilling11 and cosmetics12

Mode of Action

When water and sodium hypochlorite interact, they produce Na+ and OCl− in an equilibrium with hypochlorous acid (HOCl). Th pH affects the predominance of HOCl or OCl− in solution. As [insert citation paper] states that chlorine exists primarily as hypochlorous acid between pH 4 and 7, as opposed to hypochlorite being the most prevalent above pH 9.

Hypochlorous acid is the active component responsible for bacterial disruption by chlorine-releasing agents (CRAs). It is understood that the OCl− ion has little effect compared to undissolved HOCl.

Hypochlorous acid indiscreetly targets bacteria by chemically linking (or attaching) chlorine atoms to  nucleotide bases that disrupt the function of bacterial DNA, impede metabolic pathways in which cells use enzymes to oxidize nutrients, and release energy, and other membrane-associated activities. At certain concentrations, HOCl eradicates spores and viruses. As a sporicide, HOCl causes the spore coat to detach from the cortex, where further degradation occurs.[e1] According to Springthorpe, “CRAs also possess virucidal activity”. HOCl is an effective virucidal when fogging a confined space. Park et al describes how  “Exposing virus-contaminated carriers of ceramic tile (porous) and stainless steel (nonporous) to 20 to 200 ppm of HOCl solution resulted in ≥99.9% (≥3 log10) reductions of both infectivity and RNA titers of tested viruses within 10 min of exposure time. HOCl fogged in a confined space reduced the infectivity and RNA titers of NV, murine NV, and MS2 on these carriers by at least 99.9% (3 log10), regardless of carrier location and orientation. We conclude that HOCl solution as a liquid or fog is likely to be effective in disinfecting common settings to reduce NV exposures and thereby control virus spread via fomites”


Toxicity, flammability and compatibility of materials should be considered in selecting an appropriate disinfectant. For environmental decontamination applications within habitable spaces, clearly certain biocides are too toxic (e.g., phenolics and glutaraldehyde) or flammable (e.g., alcohols) or have the potential to leave unwanted residues on surfaces (e.g., iodophors). Hypochlorous is not flammable and not known to release harsh chemicals. Hypochlorous acid should not be mixed with ammonia-based products, as chloramines can be released.

EPA Approved Marketing Claims

The Environmental Protection Agency approved marketing claims in 2017 for Lysol’s Daily Cleanser (owned by Reckitt Benckiser), a hypochlorous acid product with the following ingredients, water (99.813%), salt (0.17%), Hypochlorous acid (0.017%). Lysol’s approved marketing claims exhibit it’s product to be gentle with no harsh vapors, safe for babies and pets, and suitable for medical applications.

  1. Suitable (for use) as a (peroxide alternative)
  2. Breaks Down to Saline Solution
  3. (Breathe Easy:) (Fragrance Free) (No Harsh Fumes) (No Harsh Chemicals)
  4. Leaves no harsh (chemical) residue
  5. No harsh (chemical(s)) (residue) (left) (behind)
  6. A (gentle) (mild) way to clean
  7. No rinsing (necessary) (required)
  8. For use in (newborn) nurseries
  9. For use in neonatal nurseries
  10. No harm after pet contact with product
  11. Fragrance Free, won’t irritate your dog’s nose
  12. No harsh fumes to irritate (pet) (dog) noses
  13. (Gentle) (Mild) (enough) to use on any washable hard, non-porous surface

Acute Oral Toxicity

A 2-year study by the National Toxicology Program was initiated to determine the potential toxicity and carcinogenicity associated with extended, direct exposure to chlorinated water or indirect chemical exposure through the formation of by-products. This study is cited for its completeness. Water containing 0, 70, 140, or 275 ppm chlorine (based on available atomic chlorine) was given to both female and male rats and mice. Further, water containing 50, 100, or 200 ppm chloramine was administered to rats and mice of both sexes for 2 years as well. The study noted that survival among treated rats and mice was similar to controls. The Environmental Protection Agency used NTP study to develop an oral Reference Dose (RfD) for chlorine. In the EPA’s Rfd report, they clarify that “the term “free chlorine” (free available chlorine, free residual chlorine) refers to the concentrations of elemental chlorine, hypochlorous acid and hypochlorite ion that collectively occur in water.” A No Observed Adverse Effect Level (NOAEL) was identified by the EPA, which states “the NOAEL of 275 ppm (13.6 or 14.4 mg/kg-day for male and female rats, respectively)”. Another hypochlorous acid study was performed that exposed rats to 14 mg/kg-day for up to 12 months (Abdel-Rahman et al. 1984). A NOAEL of 14 mg/kg-day was identified for this study. No mortality was observed. Only minor systemic toxicity was found.

[Insert: HOCl is less that acute toxicity amount]

NTP, 1992. Chlorinated and Chloraminated Water, NTP TR 392


Respiratory and Inhalation Effects

A 2-year chlorine gas inhalation study with rats showed no evidence of carcinogenicity (CIIT 1993; Wolf et al. 1995).

According to the Environmental Protection Agency an Inhalation Reference concentration (RfC) for chlorite is not recommended at this time.

Pool chlorination has been associated with a risk of developing asthma. However results of pool chlorination causing respiratory symptoms or other health effects are not consistent. Font-Ribera et al suggests that swimming did not increase the risk of asthma or allergic symptoms in British children. However swimming was associated with increased lung function and lower risk of asthma symptoms, especially among children with preexisting respiratory conditions. Goodman et al conducted a meta-analysis that noted that asthma and swimming could only be confirmed in a study of only non-competitive swimmers. The study mentions that it’s too early to draw conclusions between swimming and asthma, since the association isn’t confirmed among non-competitive swimmers. The study also notes, “Asthmatics may be more likely to select swimming because of their condition”.

Jiang-Hua Li et al mentions that chlorination is the most popular method for disinfecting swimming pool water; however, although pathogens are being killed, many toxic compounds, called disinfection by-products (DBPs), are formed. The study, with a rat model concluded that direct irritation of the DBPs to the respiratory tract, eyes and skin because these organs were in direct contacted with the DBPs, the eyes and skin might be the organs that require greater attention for permanent damage, the liver is most likely the most possible target organ of DBPs. Also that training intensity, training frequency and water choking may be the primary factors for lung damage induced by swimming, instead of chlorination.

“Nevertheless, disinfection of swimming-pool water with chlorine is an example of how a very strong oxidant such as HOCl can be tolerated by humans if the concentration is accordingly low. As a result of feeding chlorine gas into the pool water, HOCl is formed (see equation 1) and maintained at a very low concentration equivalent to 0.5 to 1.5 mg Cl2/liter (7.1 to 21.2 μM).”

With enough free chlorine and adequate ventilation to blow away the breakdown products that gas off the pool, the chlorine will break down the ammonia products until nitrogen is all that is left, which gases off the pool.

Nitrogen trichloride is the cause of most of that “swimming pool” smell. It can be highly irritating and is the cause of the lung, eye and throat irritation people experience in poorly ventilated indoor pools.

Ae Dermal Toxicity


Few animal studies addressed no- or mild-effect levels at exposure times of 10 min to 8 h. No gross or microscopic lung changes occurred in rabbits following a 30-min exposure at 50 ppm (Barrow and Smith 1975). The highest 30-min values resulting in no deaths (LC0) for the rat and rabbit were 547 ppm (Zwart and Woutersen 1988) and 200 ppm (Barrow and Smith 1975), respectively. The 60-min concentrations resulting in no deaths in the rat and mouse were 322 (Zwart and Woutersen 1988) and 150 ppm (O’Neil 1991), respectively. No deaths, but moderate to severe lesions of the respiratory tract and peribronchiolitis, occurred in rats following a 6- h exposure at 9.1 ppm (Jiang et al. 1983).

Thirty-minute LC50 values ranged from 137 ppm in the mouse (Back et al. 1972) to 700 ppm in the rat (Zwart and Woutersen 1988). The 60-min LC50 and LC01 values for the rat were 455 ppm and 288 ppm (Zwart and Woutersen 1988).

Reproductive & Developmental Effects

Chlorine administered in the drinking water or by gavage to rats or mice did not cause reproductive or developmental problems (Druckrey 1968; Abdel-Rahman 1982; Meier et al. 1985; Carlton et al. 1986).


HOCL can be synthesized through electrolysis of a dilute brine solution:

In the electrolysis process, a brine solution (NaCl + H2O) provides the chloride ion (Cl-) that is reduced (by electricity) to form chlorine gas. This process is done in water, so the chlorine gas produced chemically reacts with water present to produce hypochlorous acid (HOCl), hydrogen ion (H+) and chloride ion (Cl-). The reaction is as follows:

2Cl-      Cl2                                 (electrolysis)
Cl2  +  H2O     HOCl  +  H+  +  Cl-            (hydrolysis)

This process utilizes an electrochemical chambered cell or group of cells that have electric current passed through the aqueous NaCl solution.
OCl-   +   H+       HOCl                       (lowering  pH)

To be continued……

Your HOCL caregiver,

Michel van Schaik,  info@aquaox.net

For more information visit www.aquaox.com

Tags: , , , , , ,

One Response to “HOCL as an antimicrobial”

  1. Sep Snyder Says:

    Thank you for the information. I am a fan of Aquaox!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: