A solution of diluted bleach was shown to not be an effective antibacterial agent in vitro for eradicating Staphylococcus aureus, a common skin irritant for patients with atopic dermatitis, according to study results published in the Journal of Allergy and Clinical Immunology.

Researchers used 3 strains of S aureus on nutrient-rich surfaces to examine the impact a diluted bleach solution of sodium hypochlorite at concentrations between 0% and 0.01% would have on the bacterial colony growth. The bleach solution baths were only effective at a level above 0.03%, which is a level cytotoxic to human cells. Researchers expanded their study and included 2 strains of Staphylococcus epidermidis and found this bacterial colony growth was also not inhibited by a bleach solution appropriate for human cells. The same results were found when S aureus was tested on pig skin to mimic human skin glands and follicles, which meant the bleach bath had no antibacterial impact on the bacteria.

Diluted bleach baths are often prescribed to patients with atopic dermatitis to reduce bacterial colonization that could lead to infections. Based on these results, the bleach bath did not display antibacterial properties by reducing the growth of the bacterial colony. These findings are not meant to refute bleach bath therapy, only to provide evidence that the positive aspects of the therapy might not be directly related to the antibacterial mechanism of the bleach solution.

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Further research needs to analyze the impact the bleach bath has on the skin microbiome, the inflammatory process of atopic dermatitis, and cysteine residues of the inhibitor of nuclear factor-κB.

The researchers concluded “[s]oaking in a dilute solution of household bleach (0.005%) is not an effective antibacterial treatment despite its common use to suppress S aureus colonization on the skin of patients with atopic dermatitis.”

Disclosure: One author reports being a consultant with equity interest in MatriSys Bioscience and Sente Inc. and a co-founder of MatriSys Bioscience.

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Sawada Y, Tong Y, Barangi M, et al. Dilute bleach baths used for treatment of atopic dermatitis are not antimicrobial in vitro [published online January 21, 2019]. J Allergy Clin Immunol. doi: 10.1016/j.jaci.2019.01.009