QUESTION

I’m trying to be more eco-friendly and have heard that oregano oil cleans and disinfects kitchen countertops as well as typical supermarket kitchen cleaners. Does it really kill germs—including salmonella and E. coli?

ANSWER

Good question! People have been using oregano essential oil for medicinal purposes for centuries because of its antimicrobial properties. You also can find dozens of commercial “natural” household cleaners that contain oregano oil…plus recipes to make your own. But that doesn’t necessarily mean that oregano oil—at least on its own—is sufficient for eliminating the microbes that can give you food poisoning. Perhaps best known as an herb to sprinkle on pizza, oregano and especially the oil made from the herb contain a high concentration of the antibacterial and antifungal phenols carvacrol and thymol. Studies have demonstrated oregano oil’s antimicrobial effects against dozens of pathogens in laboratories. In one trial, a hand-and-kitchen cleanser made with oregano oil killed several food-borne bacteria, including Salmonella, E. coli and Staphylococcus aureus.  However, it should be noted that the researchers emulsified the oregano oil in a liquid detergent solution—meaning the oil was made to be evenly dispersed within another cleaner (detergent) that has antimicrobial properties of its own. So it’s hard to know how effective oregano oil alone would be. While oregano oil hasn’t been specifically studied for how well it works on cleaning kitchen surfaces, plenty of studies have shown its antibacterial and antifungal activity in a research setting. Oregano oil also doesn’t carry the risks associated with triclosan, the active ingredient in many kitchen cleaners that is known to contribute to drug-resistant bacteria and may disrupt hormones in people. If you want to make your own eco-friendly antibacterial cleanser, you might include oregano oil, but don’t rely on it exclusively. And be sure to use the most powerful type of oregano oil. Here are tips for making a household cleaner including oregano oil…

  • Use the right oregano oil. There are many species of oregano, but Origanum vulgare has the highest concentrations of carvacrol and thymol.
  • Use an emulsifier. Oregano oil isn’t soluble in water, so don’t use a formula that calls for putting a few drops of oil in water—it won’t mix, so you won’t have an even distribution of the antibacterial properties. Instead, first blend 10 to 15 drops of the oregano oil with one tablespoon of an emulsifier such as liquid castile soap, and then add it to a cup of water or vinegar. (Adjust the amount of oregano oil as needed to arrive at the desired strength.)
  • Extend its shelf life. Oregano oil is relatively stable and should stay potent for three years. However, exposure to light, oxygen and heat speed up oxidation, which will reduce its efficacy. To minimize oxidation, mix up small batches that will be used quickly…fill bottles (brown glass is best—to avoid possible contamination from plasticizers that are soluble in oregano oil and to minimize light exposure) as close to the top as possible to reduce the amount of oxygen that comes in contact with the solution…and store in a cool, dark place.
  • Be safe. Oregano oil is generally regarded as safe, however, people with mint allergy, pregnant women and young children should avoid direct contact with undiluted oregano oil. The concentration in a typical sprayed surface cleaner is low enough that it shouldn’t pose a risk to humans or animals.

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