Powdery and downy mildew are the two main types of mildew. Powdery mildew settles on flowering plants like roses, while downy mildew settles on agricultural plants like potatoes.
Mildew is caused by mold, which are plants that require moisture and warm temperatures to grow. Mold develops on non-synthetic fabric, wood and paper.
Where you find mold, you'll usually find mildew. In homes, this usually occurs in damp, warm areas with poor light and poor air circulation. Closets, cellars and bathrooms are the usual culprits.
Although mildew removers don't work on paper and fabrics, mildew on a hard surface can be eliminated by spraying a mildew remover solution onto it. Bleach solutions effectively kill mold and mildew as well.
Keep any place where mildew is likely to grow--such as a closet or bathroom--as clean as possible. Eliminate dampness by heating the room for a little while; then open doors and windows, or use air conditioners and dehumidifiers to dry the air or cool it down so that the moisture is removed. Ventilate closed off or poorly ventilated spaces by opening doors and windows and using electric or exhaust fans (in closets, make sure clothes are dry and hang them loosely to allow air to circulate around them).
Inhaling or ingesting mildew can trigger asthma or allergies (even in people who have no allergies, if the concentration of mildew and mold is high enough). For people who have chronic lung or immune system problems, mildew and mold can increase the likelihood for fever, infections and pneumonia-like symptoms.