Mildews are fungi, organisms that thrive in humid or damp places.
The U.S. Environmental Protection Agency describes mildew as “thin coatings of powdery fungi that can grow on a damp surface.”
Mildewed bathroom tile may be cleaned with a solution of five parts water to one part chlorine bleach applied to tile and grout with a scrub brush. Wear protective gloves and use a fan to ensure adequate ventilation whenever working with any cleaning solution containing bleach. Allow the solution to work for a few minutes, then rinse thoroughly and dry all surfaces.
On painted or sealed surfaces, a household disinfectant will remove mildew. You can also try a solution of borax and water, followed by rinsing. According to the EPA, borax is an effective mildew remover and short-term preventive that is less toxic than the organic chemicals traditionally used to treat mildew outbreaks.
Mildewed clothing should be sun-dried, then vacuumed with a crevice tool to remove blooms. Do this outside to reduce the number of airborne spores indoors. Securing an old nylon stocking over the crevice opening will keep clothing out of the vacuum hose. Pre-treat mildew spots with diluted chlorine bleach or commercial products containing enzymes as appropriate, and then wash garments in the hottest water safe for the fabric.
Sunlight will dry out the leather used in footwear, so avoid that approach when treating mildew on shoes or boots. Using a paper towel or cloth, dab rubbing alcohol onto blooms until they’re gone. Polish the shoes or boots immediately.
Mildew has a nasty habit of recurring if you don’t take steps to reduce humidity and moisture in your home.
For more information on reducing humidity and moisture, see the EPA article, "What You Need to Know about Mold."