Deter mice with strong chemical smells. Natural chemicals, such as ammonia and peppermint oil, can be used just as effectively as most commercial mice repellents.
Cats are natural predators to mice, so most rodents have adapted to avoid places that smell like cat urine. Cat urine smells strongly of ammonia, so for a natural repellent, ammonia is the most effective. Less noxious but also effective are peppermint oil, mothballs and fabric softener sheets. Most modern commercial repellents use natural ingredients that irritate a mouse's nervous system. They also undergo testing to ensure they are safe for the environment and for use around pets and children.
To prevent mice, apply the repellent in areas where pets and children are not likely to ingest it. Use it in places where mice will hide, such as in a basement or garage and around garbage cans. When using chemicals like ammonia, be sure to ventilate the area of application and avoid overexposure to the toxic fumes.
Ammonia can be diluted with water and used to wash areas frequented by mice. It is also common to keep a small, open jar of ammonia in an area where mice will smell it. Always be sure to read instructions and warning labels when using toxic chemicals and commercial pest repellents.