Mold and mildew have many similar characteristics, but they are different types of fungi, and are often different in color and texture. They are often mentioned together, as both mold and mildew can grow in many of the same moist and warm locations. Mildew is often found more often than mold in showers, paper, and fabrics, however, and mold is usually found more often than mildew in foods. They can sometimes be difficult to tell apart, as both spread out from spores. Mold is often black, green, red, or blue in color while mildew is usually gray or white.

The two main types of mildew are powdery and downy. Powdery mildew is commonly found on roses and other flowering plants, and usually looks like white or gray splotches. It is created by an ascomycota type of fungus. Downy mildew is from the oomycota type of fungus and is found in agricultural products such as grapes and potatoes. It's appearance varies from plant to plant, with some common indications being leaf spots and distortions, downy patches, and crystalline spores that may look like sugar.

Mold often looks fuzzy or slimy, depending on the type. It can also appear in many different colors. On a wall or ceiling, some types of mold may appear to be irregularly shaped spots of black or gray.

Some molds have toxins called mycotoxins that may cause an allergic reaction or other illness in some people. Symptoms of a mold allergy may include headaches, asthma, and coughing. Irritation of the eyes and throat may also occur as a result of breathing mold toxins. Molds are not always harmful; the antibiotic penicillin was created from the mold of the same name.

Both mold and mildew thrive in damp environments. Keeping areas dry is the most important preventative measure to help eliminate fungi. Bathrooms are a prime source of mold and mildew as not only are they often damp, but they also usually do not have a lot of ventilation.

Moldy food should not be eaten. A mildew infestation on paper and some fabrics cannot be scrubbed off, but a mildew remover can usually get rid of mildew on harder surfaces such as surfaces in bathrooms. Some mold and mildew removal products should not be used by asthmatics or in an area that is not well-ventilated. Bleach solutions are often effective in killing both mold and mildew. In situations where there is serious mold growth, however, a professional may be needed to clean the space and repair any damage.