Bleach is a basic solution of sodium hypochlorite and a potent disinfectant when used in sufficient concentrations. It kills yeasts, although like many other disinfectants, it's less effective against surface-adhering films called biofilms. Increasing concentration and exposure time aid in its effectiveness. Its main disadvantage is its corrosive nature, which limits its use.
Yeast are a diverse group of fungi. All of them are unicellular, meaning they have only one cell. The most famous yeast is Saccharomyces cerevisiae, used by humans for thousands of years to make bread and beverages containing ethanol. The most infamous yeast is Candida albicans, the culprit behind vaginal yeast infections and diaper rash. Aside from these two species, however, there are many others. Only a handful of them cause disease; food spoilage is another potential concern with some species.
Scientists have conducted various experiments involving sodium hypochlorite and yeast. A 2011 study published in the Journal of Food Process Engineering compared the effectiveness of sodium hypochlorite against planktonic (free-floating) and biofilms of different species. At concentrations as low as 200 parts per million, sodium hypochlorite was highly lethal to the planktonic yeasts. The biofilms, however, were more difficult to destroy and required higher concentrations of sodium hypochlorite. Sodium hypochlorite, however, was more effective than quaternary ammonium compounds, which are also used as disinfectants.
Yeasts like Histoplasma capsulatum, Candida albicans and various Cryptococcus species have the potential to cause disease in humans. A study published in 2004 in the Journal of Medical Microbiology found that a 1.2 percent solution of sodium hypochlorite was highly effective in killing multiple species of disease-causing yeasts in culture while UV light and hydrogen peroxide were not effective. The authors also found, however, that treating a biofilm with sodium hypochlorite for five minutes was not effective in killing them. Longer exposures or sodium hypochlorite at a higher 12 percent concentration could destroy the biofilms, but this higher concentration is more toxic to humans and hence more dangerous to use.
Household bleach is a 5.25 percent solution of sodium hypochlorite. Scrubbing or wiping a surface with bleach will be sufficient to kill any yeast you might encounter; disinfecting a clean surface is easier than disinfecting than a dirty one. Note that bleach only has an effective lifespan of about six months -- less if the container is frequently left open. Regardless of its effectiveness against pathogenic yeast, never try to drink bleach or apply it to any part of your body; it's not only toxic to yeast but potentially toxic for you as well.
- Louisiana Department of Health and Hospitals: Sodium Hypochlorite
- Journal of Medical Microbiology: Efficacy of Antiseptics and Disinfectants on Clinical and Environmental Yeast Isolates
- Yeast Genome: What Are Yeast?
- Journal of Food Process Engineering: Efficacy of Sodium Hypochlorite and Quaternary Ammonium Compounds on Yeasts
- University of Kentucky Environmental Health and Safety: Laboratory Disinfectants
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