A ‘short’ explanation by Dr Ulrike Ziegner, MD, PhD, Board Certified Allergy Immunology

Figure 1: Mold sample from nasal tissue

Molds are microscopic fungi. They are among the most widespread of all living organisms we know. They number in the 10’s of thousands of varieties. Unlike plants, mold is unable to produce its own food from sunlight and air, so it lives on plant and animal matter that it decomposes or depends upon for nourishment.

There are many common varieties of mold including bread, fruit, vegetable and other common elements of decomposition of organic materials. Certain types of molds produce penicillin and other antibiotics. Mold has extreme variations. Some molds are necessary components of agriculture and food production, while other types of mold produce potent toxins and can become a source of disease. A number of molds reproduce by releasing spores into the air. When inhaled, and these spores may become a problem by producing allergic symptoms.

Figure 2: Mold on Peach

Most mold is found in moist environments. Unlike pollen, it does not have a strictly limited season. Mold growth is encouraged by warmth and high humidity, and is therefore most prevalent during the spring-summer and early fall. Mold is found both indoors and outdoors. It is present in outdoor air and can exist even in winters moist soil. Mold grows best in shady, damp, areas and on decaying leaves or other vegetation. Outdoor mold becomes widely dispersed through the air and can then enter the home via air currents, pets, shoes, clothing, etc. Indoor mold is usually produced and nourished in the higher humidity areas such as showers, basements, under sinks and in crawl spaces. Another significant source of mold may be found in the circulation vents of automobiles. See below.

Mold sensitive individuals should avoid exposure to areas that may contain high counts of mold spores as mentioned above. A facemask may be worn when exposure is unavoidable. It is important to control these indoor areas of humidity and warmth. Use of an Air Conditioner or dehumidifier is suggested. The additional use of exhaust fans over cooking areas and around showers is helpful in control.

Figure 3: Stilton cheese, edible

    • Keep humidity low (as close to 35% as possible), but never more than 60%.
    • Use an air conditioner or dehumidifier with the windows closed in the summer. Be careful to balance your air conditioner for size. Too large a unit may cool the air before dehumidification. Dehumidifiers must be cleaned regularly and emptied often.
    • Special HEPA filters can be used to help trap the air-born allergens throughout the home.
    • Never use a humidifier or swamp cooler. These are known sources of mold growth and require frequent & thorough cleaning.
    • Very tight insulated homes may need to have mechanical ventilation installed to prevent trapping moisture inside.
    • Use exhaust fans to remove water vapor when cooking.
    • Check refrigerators frequently for signs of mold growth around door gaskets, in the drain pan underneath, and on foods stored too long in fruit and vegetable drawers.

    Figure 4: Mold growing on shower curtain

    • Use exhaust fans or open windows to remove excess humidity after showering.
    • Wash shower curtain, bathtub and tiles with soap frequently.
      • Be cautious about the use of products that contain chemicals like lime-away, and caustic substances that may contain volatile odors.
    • Repair damaged caulking and grout. These problems allow water into unintended areas where mold can then be harbored.
    • Never carpet bathrooms.
    • Keep dryer vent free of lint plugs.
    • Dry clothing immediately after washing.
    • Avoid the use of fabric softeners in the wash water (and the dryer for asthma patients). They can aid in the growth of mold around the seals of wash areas.
    • Use dehumidification. Repair/correct seepage or flooding problems and avoid the use of carpeting that cannot be kept thoroughly dry.
    • Cover any dirt with a plastic vapor barrier.
    • Keep basement free of dust and remove moldy stored items. Avoid storing anything likely to harbor mold (including clothes).
    • Use paint with mold inhibitors added. Make sure that basement walls are ‘sealed’ from the OUTSIDE.
    • If you have allergies then avoid these areas.

    Figure 5: Mold in auto A/C cabin drain

    • Remove carpeting completely if possible. Encase mattress and pillow cases with impermeable zippered covers.
    • Keep condensation on windows wiped dry in the frames. Books, leather products, stuffed toys, wood paneling, and wall-paper paste also support mold growth and should be avoided.
    • Mold grows well in closets which are damp and dark. Dry all shoes, clothes and boots thoroughly before placing them in the closet. Keep closet doors open when they need drying.
    • Limit indoor houseplants, and be careful to select those that do not grow mold easily.
    • Spores may become airborne when plants are watered. Take live plants out-of-doors frequently.
    • Mold may be present in the bark of wood. Use caution when burning indoor fires in the fireplace. Avoid live Christmas Trees.
    • Purchase a medical grade HEPA filter that removes mold spores. Mold is usually found between 2.5-15 microns. A charcoal filter may be required for certain types of VOC’s associated with certain species of mold. Inexpensive table top, and ‘cleanable’ filters are not effective. ELECTROSTATIC FILTERS SHOULD BE AVOIDED. They cause harm to the delicate tissue in the lungs.
    • If you are a mold sensitive individual, avoid cutting grass and raking leaves. Use a facemask if unavoidable! Avoid exposure to soil, compost piles, sandboxes, fertilizers and barns. Prune or cut trees to avoid shading of any areas of the home susceptible to moisture build-up. Eliminate Ivy growing in close proximity to the home.
    • Correct any drainage problems near the home, and monitor sprinkler systems for overspray that hits the homes’ exterior repetitively.
    • Automobiles A/C systems can be a significant source of mold. When there is a temperature  change (ΔT) from the inside to the outside of more than 10 degrees. This combination along with the warm humid air exhaled by the autos occupants cause a build-up of humidity. If the A/C system is allowed to remain in the on position when the ignition is turned off, the system remains open and this moisture condenses in the a drain pan that is usually inaccessible.

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