Mice and rats are a difficult problem to solve because if you don't want to kill or harm the mice, there aren't many things you can purchase specifically made to repel them. Luckily, there are a few substances you can purchase at your local drugstore or grocery store that may do a better job in repelling mice than most products sold specifically for getting rid of rodents.
Mice do not like the scent of mint leaves, mint oil or peppermint oil. Although it's impossible to coat your entire house in mint, it is possible to leave mint where mice tend to enter or frequent. Try planting mint leaves around the outside of the house, at the foundation level where mice tend to enter and exit. A mouse will be less likely to want to enter your house if it smells like mint, and will most likely pick a different house instead.
Inside the house, you can place mint leaves or dab peppermint oil in drawers, corners, under the refrigerator and anywhere else mice tend to frequent. Luckily, mint smells delicious to humans, so your house will smell lovely and you can avoid having a rodent problem at the same time. As soon as the mint leaves lose their scent, replace them. As soon as you can't smell the oil, put more oil in its place.
Mice, like moths, dislike the smell of mothballs. They will not want to populate or make a home in an area that has mothballs, so place lots of mothballs in the corners of your garage and basement, where mice tend to hide and live.
If you don't mind the smell of mothballs yourself, you can place them in your kitchen drawers or underneath your refrigerator. The upside to mothballs is that they will stay potent longer than mint leaves or mint oil, which need to be replaced more often. Mothballs, however, have a strong smell that most people dislike.
Steel wool is effective in keeping mice out of even the largest openings. Stuff steel wool into every pipe hole, crack or crevice where you think mice are entering your home. You can use steel wool both inside and outside the house, and it does not need to be replaced unless it is in a moist area and rusts.
Mice are not able to eat through steel wool and they do not like how it feels. If they find that steel wool has been stuffed into their pathways, they will not use the hole or path.