to mask the scent of any tasty morsels that have been missed when cleaning. It also gives the house a lovely smell, and is not toxic, unlike many synthetic chemical treatments. You can get peppermint oil in most health food stores and even some major grocery stores. [2] Place a drop or two on a cotton ball. Place a cotton ball under or near your garbage can to deter mice from getting into it. Place the cotton balls in areas where mice are likely to enter your house, by doorways, or heat vents, etc. Peppermint oil cotton balls need to be replaced after 5 - 7 days, depending upon the quantity of oil you put on it. Try growing peppermint plants near the entryways. You can use the