There is a fair possibility that your "For You" page has given you the recipe for this already: 2 tablespoons borax, ¼ cup vinegar, 2 cups hot water, shake, spray, done. Mississippi State University Extension Service does indeed list this exact formula as an “All-Purpose Cleaner” in its healthy cleaning recipes, adapted from Clean and Green by the University of Arkansas Division of Agriculture. In other words, this became a wellness trend way after it had already been a piece of agricultural extension advice. And this is precisely the reason why this one deserves a closer look.What is really going on in that spray bottle?Borax, or sodium tetraborate, is a borate salt, while vinegar contains acetic acid. When the two are mixed, they do react: research using 5% acetic acid found that borax can react with acetic acid to form boric acid and sodium acetate. So this is not simply a case of two ingredients retaining all of their original properties after being poured into the same bottle. The resulting solution has different chemistry from either borax or vinegar on its own.That does not mean the mixture is useless as a household cleaner, especially since Mississippi State Extension specifically publishes it as an all-purpose cleaning recipe. But it is more accurate to describe it as a general cleaning solution than to suggest that the mixture creates a special chemical effect that “breaks surface tension” in the same way as dish soap. It may be a proper decent all-purpose wipe cleaner for ordinary household grime, but its cleaning performance should not be confused with disinfection.But is it a disinfectant?This is the bit that you may miss most of the time. Much of the online buzz about creating vinegar sprays raises the hope that they will "kill germs," and that conclusion is not supported by the recipe itself. A 2014 study titled “Acetic Acid, the Active Component of Vinegar, Is an Effective Tuberculocidal Disinfectant,” published by Claudia Cortesia et. al, in the journal mBio, found that a 6% acetic-acid solution killed Mycobacterium tuberculosis after 30 minutes of exposure. The study also found that some nontuberculous mycobacteria required 10% acetic acid for 30 minutes to achieve at least a 6-log reduction. Those experimental concentrations and exposure times are important. The study was not testing the Mississippi State household recipe, and its findings should not be read as evidence that ordinary household vinegar, or a heavily diluted vinegar-based cleaner, is a general-purpose disinfectant. The researchers also noted that they did not assess acetic acid's activity against viruses and fungi.Different flavours of vinegar. Image credits: Wikimedia CommonsStandard grocery-store vinegar is already only about 5 percent acetic acid, and the MSU recipe dilutes vinegar substantially further once it is mixed with two cups of water and the other ingredients. It therefore falls well below the 6% acetic-acid concentration tested against M. tuberculosis in the 2014 study. It is also more accurate to refer to EPA rather than FDA when discussing household surface disinfectants in the United States. EPA regulates disinfectants as antimicrobial pesticides and requires registered products to meet specific efficacy standards for the microorganisms claimed on their labels. The exact efficacy requirement depends on the organism, product and use claim, so it is too broad to say that every disinfectant simply has to meet one universal “99.999 percent” threshold. EPA also stresses that users should follow the registered product's label, including its specified contact time.The borax caveatLet's look at the more serious note. Borax is not a "natural mineral" in the same jargon-laden sense that it may be often sold as, and is, in fact, a registered pesticide. The National Pesticide Information Center is a joint project between Oregon State University and EPA that says boric acid and its sodium borate salts, including borax, have been on the U.S. marketplace since 1948 and that "keep out of reach of children" is a common warning on product labels.Borax can irritate the eyes and respiratory system, and exposure should be taken seriously rather than dismissed because the substance is marketed as a household or “natural” product. That is particularly relevant to a spray bottle. NIOSH lists inhalation as an exposure route for borax and identifies irritation of the eyes, skin and upper respiratory system, including coughing and breathing difficulty, among possible symptoms. The sensible approach is therefore to avoid deliberately creating or breathing a fine mist, use the product according to the label directions for the borax being used, and keep the mixture and the original borax product out of reach of children and pets.So, should you actually make the spray?Yes, it can be used as a household cleaner because Mississippi State University publishes this exact formulation for that purpose. But its usefulness should be understood in those terms: cleaning, not disinfecting. It is a cheap, non-fuming alternative to some commercial degreasers, and for people who prefer simpler household-cleaning formulations, it can be a useful everyday cleaner for appropriate surfaces. It is not a substitute for a registered disinfectant when disinfection is needed, and it should be stored and used according to the product label, especially around children and animals.Borax-based washing detergent. Image credits: Wikimedia CommonsA cautious step you can take here is not to blindly trust the recipe simply because it is circulating online, but also not to dismiss it outright: use it for the cleaning purpose for which Mississippi State Extension recommends it, follow the borax product's safety instructions, and reach for an EPA-registered disinfectant when actual disinfection is required.