Thieves essential oil is a plant-and mineral-based disinfectant that uses clove, lemon, eucalyptus and rosemary oil (as well as cinnamon bark). Its manufacturer, Young Living, uses the blend as a base for biodegradable household cleaners and personal hygiene products.
According to Young Life, the use of essential oils as antidotes to disease dates to the time of the Black Death in Europe. Thieves, the story goes, would use the essential oils so that they could rob the dead with impunity. When the the group was caught, a judge offered them their freedom in exchange for their secret to avoiding infection. Whether or not this story is indeed historically accurate, a 2000 study published in "Skin Pharmacology and Applied Skin Physiology" demonstrated that at least eucalyptus oil has antifungal properties.
Usage on granite
While you should test Thieves essential oil cleaner on a small, inconspicuous area first, the cleaner should be safe for granite countertops. You should dilute the cleaner at a ratio of one half tablespoon to two cups water for medium degreasing, increasing or decreasing this ratio depending on the job.
Thieves essential oil products use biodegradable ingredients and food-based oils, so their environmental impact is considerably lower than traditional cleaning products.
The disinfectant properties of Thieves products' ingredients have not been evaluated by the Food and Drug Administration (FDA). Bear in mind that some people may have an allergic reaction to certain essential oils, so start off small if you decide to switch from traditional cleaning products.
Until the FDA or a major study has proven that it is an effective disinfectant, Thieves essential oil should not be used to clean areas where incomplete disinfection is likely to spread disease. Examples include hospitals and nursing homes, public bathrooms and commercial kitchens.