A scientific review of the chemistry of wound healing and hypochlorous acid, why purity of the molecule in a wound cleansing solution matters and why hypochlorite is no longer a must use ingredient.

Objective: Chlorinated species such as molecular chlorine, hypochlorous acid, and sodium hypochlorite all have antimicrobial properties, yet these differ in the cellular response they elicit, which is important in the context of wound healing.

The purpose of this study is to review the laws of physical chemistry, and published literature to reach conclusion on the most desired species from the three mentioned here.

Methods: We did a survey of published literature on two key subjects, which is the toxicity of hypochlorite anion, which is present in Dakin’s solution as the predominant species, and hypochlorous acid solutions.

In particular, we were interested in solutions that have very low concentrations of the hypochlorite anion (commonly present in Dakin’s solution or bleach) and solutions that have hypochlorous acid above 250 ppm which is present in some wound solutions where the concentration of hypochlorous is the highest amongst commercially available products.

Result: The cytotoxicity of the hypochlorite species is well published. This cytotoxicity was observed in Dakin’s solution that was diluted to 0.00005%, which corresponds to 5 ppm. Hypochlorous acid, too, can be cytotoxic, at very high concentrations, however, at 250 -350 ppm seems to be completely benign. The antimicrobial preservative efficacy at that 250-350 ppm hypochlorous acid is high, with most tested bacterial and fungal species tested perishing in a matter of 15-30 seconds.

Conclusion: Eukaryotic cells have protective mechanisms to be able to handle hypochlorous acid at a concentration such as 250-300 ppm. Prokaryotes such as unicellular microbes have not evolved to be protected against hypochlorous acid. However, eukaryotic cells do not seem have protective mechanisms against the hypochlorite, even at low concentrations, and thus are affected by the presence of hypochlorite anion.

Trademarked Items (if applicable):

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