What is Mold?

- Aug 25, 2017-

A mold is a type of fungus: a plant-like organism that does not use photosynthesis to produce food, but instead obtains it directly from its surroundings. Molds can display themselves in a variety of colors, such as the familiar green covering often seen on bread or fruit, but this is due only to the reproductive part of the organism — the fungal equivalent of flowers and fruit. The main part of the fungus consists of a network of thin, transparent filaments known as hyphae, which is much less visible.


These fungi can grow on a variety of materials, including soil, decaying plant parts, food, fabrics, and damp walls. They reproduce by releasing huge numbers of tiny spores, which are very tough, and can withstand drying and freezing. Although mold can be a nuisance, and occasionally a health hazard, they can also be useful; they are essential for the breakdown of dead organic matter in the natural environment, they are a valuable source of antibiotics and drugs, and are employed in the production of some foods.

In the Home

Humans have lived with molds for millennia, but in a modern domestic setting, they can cause problems. The black type that forms on damp surfaces such as bathroom walls is unsightly, and may cause damage to the structure. When large quantities of spores become airborne, they can cause a variety of unpleasant symptoms. Some people are allergic to these fungi, and may experience coughing and sneezing, eye irritation, and skin rash. People with asthma, however, may experience more severe problems, such as breathing difficulties.

The spores are constantly present in the atmosphere, and little can be done about them; however, they do not pose any direct threat at the low concentrations normally found in outdoor air. It is when they are produced in large amounts in an enclosed, indoor space that they may have health effects. While spores can survive harsh conditions, the molds themselves require moisture and some degree of warmth to grow. Damp areas in the home are ideal for them, especially if they have poor air circulation and receive limited amounts of natural light, so they are common in bathrooms, basements and attics. When spores land on a damp, indoor surface, they can germinate and form mold that spreads rapidly.

Dealing with Molds

If a homeowner is tackling a mold problem himself, it is in his best interest to invest in some kind of face mask to avoid inhaling particles and spores. A surgical mask, or the type used by carpenters to keep from inhaling saw dust, works well for this task. A long sleeved shirt and long pants should complete the protective outfit.

Mold can be removed by scrubbing the area with warm water and detergent, then allowing it to dry. An additional step of disinfecting the area with a solution of 1 gallon of water (about 3.8 liters) to 1/4 cup (about 60 milliliters) of bleach and then letting it air dry is recommended. This step can be repeated to ensure that most, if not all, of the mold is eliminated. There are also commercial removal products available that are normally sprayed onto the affected area.

To permanently get rid of the problem, however, the source of dampness must be eliminated. The most common reason for dampness is high humidity in places such as bathrooms or sometimes kitchens, and as a result of hanging damp clothes up to dry indoors. Solutions include improving ventilation, dehumidifiers, air conditioning, and drying clothes outdoors, if practical, or using a tumble drier. Other sources of dampness may be leaking roofs, leaking pipes or seepage from wet ground, which may require professional help to fix.


The toxins produced by some species of mold are very effective at killing bacteria, and this discovery led to the development of antibiotics. The first such compound to be discovered was penicillin, in 1928. It revolutionized the treatment of many infectious diseases and since then, a number of other compounds of medical interest have been obtained from these fungi.

Some types are also used in the manufacture of food. They are essential to many types of cheese, such as Camembert and Stilton. The production of soy sauce depends, at an early stage, on the growth of a type of mold on the raw material.