Mold Spores and Allergies Mold Spores and Allergies
National Institute of Environmental Health Sciences

Several molds that grow both indoors and outdoors, produce allergenic substances. These allergens can be found in mold spores and other fungal structures (e.g. hyphae). There is no definite seasonal pattern to molds that grow indoors. However outdoor molds are seasonal, first appearing in early spring and thriving until the first frost.

Indoor molds are found in dark, warm, humid and musty environments such as damp basements, cellars, attics, bathrooms and laundry rooms. They are also found where fresh food is stored, in refrigerator drip trays, garbage pails, air conditioners and humidifiers.

Outdoor molds grow in moist shady areas. They are common in soil, decaying vegetation, compost piles, rotting wood and fallen leaves.

Preventive Strategies:

– Use a dehumidifier or air conditioner to maintain relative humidity below 50% and keep temperatures cool.

– Vent bathrooms and clothes dryers to the outside, and run bathroom and kitchen vents while bathing and cooking.
Regularly check faucets, pipes and ductwork for leaks.

– When first turning on home or car air conditioners, leave the room or drive with the windows open for several minutes to allow mold spores to disperse.

– Remove decaying debris from the yard, roof and gutters.

– Avoid raking leaves, mowing lawns or working with peat, mulch, hay or dead wood. If you must do yard work, wear a mask and avoid working on hot, humid days.