Bacteria live everywhere, from the surfaces in our homes to the insides of our bodies. Some bacteria are beneficial to human life; others cause harm. Leaving a moist sponge in the bathtub day in and day out gives some of the harmful germs a hospitable place to set up shop.
Loofahs are especially vulnerable to bacterial growth. These natural sponges have many nooks and crannies that -- especially when moist -- tend to invite bacteria. Additionally, dead skin cells commonly found on loofahs provide food for bacteria, giving them even more reason to move in. In fact, one study found that the amount of bacteria like P. aeruginosa, which causes a variety of infections, grew exponentially in 24 hours when exposed to a loofah sponge. The study's authors also found that soaking the sponge in a bleach solution on a regular basis killed off the bacteria, and thus helped to prevent infections [source: Bottone].
The same risks apply to other types of sponges, too. Even plastic mesh bath poufs can become infected with bacteria and lead to rashes on the skin. One such rash, called folliculitis, is an infection of the hair follicles. Mild cases of folliculitis often look like clusters of small, red bumps around hair follicles, and symptoms of folliculitis include itching and tenderness [source: Mayo Clinic]. Although such cases normally clear up with home treatment, if the area worsens or does not improve within three days, you should seek medical attention.
Bacteria aren't the only thing that can grow on your bath sponge; mold can also be a problem. Continue to the next page to learn more.