Bacteria can grow in shower heads, so better keep yours clean. Shower heads can be kept fresh and clean with some white vinegar. Start with filling a plastic bag partway with white vinegar. Then, place it over the shower head until the entire fixture is immersed in the vinegar and fasten around the neck of the shower head with a piece of string or twist ties. Let it soak for several hours — but if you have a different type of shower head (brass, gold, or nickel-coated) you should only keep in the vinegar for half an hour.