There are myriad opinions about how to sanitize kitchen sponges, ranging from soaking them in bleach (yuck!) to zapping them in the microwave to using the hottest setting in the dishwasher to kill germs and bacteria. Whatever method you choose, one thing we all should do is rinse the sponge after using it and squeeze it as dry as possible. Then place it where it can completely dry out (like on a soap dish with slats). A damp sponge is an unhealthy one, since that pool of water will just become a breeding ground for germs and bacteria.
ANDREWS MCMEEL SYNDICATION