Frequent Herbs for Health contributor Laurel Vukovic, in her book 1001 Natural Remedies, has several helpful, nontoxic suggestions for combating pesky ants. First, try a mix of 1/4 cup dried peppermint leaves (Mentha piperita), 1/4 cup powdered cayenne (Capsicum annuum) and 1/4 cup borax. Sprinkle the mixture liberally around the area where ants are entering your home to help deter ants.
Another option is to use essential oils. Try placing a few drops of peppermint, spearmint or citronella oil on a cotton ball. Put the cotton ball in areas where you have seen ants. Renew the oil every two days to keep the scent strong.
Finally, you can try a homemade ant trap. In a screw-top jar, mix 3 cups water, 1 cup sugar and 4 teaspoons boric acid. Poke holes in the jar lid and place the jar near ant trails (keep out of reach of children and pets).
Source: Vukovic, Laurel. 1001 Natural Remedies. New York: Dorling Kindersley, 2003.