It's a common fact that sponges are notorious for spreading bacteria, so they should be cleaned often. The easiest way is to microwave a thoroughly soaked sponge (a dry item might cause a fire) for about 30 seconds to 1 minute or so, to generate steam... Open the door once it's done and let cool before handling. You can also throw them in the dishwasher. Sponges should be thrown away about once a month. Have any other tips? please share!