“Although toxic mold has received much media attention lately, toxic reactions caused by fungal exposure have not been found to be a significant health problem,” said lead author Jay M. Portnoy, The Children’s Mercy Hospital in Kansas City, Mo. “The more common household molds, when in the presence of moisture, can proliferate and cause problems and health effects that are generally due to allergy or irritation to fungal substances.”

Fungi, including molds, are spore-producing organisms that comprise some 25 percent of the earth’s biomass and function as decomposers of organic material. The most common fungi found in homes include Cladosporium, Aspergillus, Penicillium, Alternaria, basidiospores, Chaetomium, Periconia and Stachybotrys.

According to the report, fungal allergy is best identified by testing for the presence of mold-specific IgE antibodies, combined with a history of symptoms following exposure. Once the specific IgE has formed, subsequent exposure to the fungus can result in an allergic reaction. Exposure to fungi has been linked to a wide range of illnesses, including asthma and rhinitis. More than 80 types of mold have been associated with respiratory tract disorders.

“A number of studies have suggested that exposure to indoor fungi can trigger allergy symptoms. Fungal exposure is also associated with exacerbations of asthma, although it remains unclear that this exposure causes the disease,” Dr. Portnoy said.

Adverse health symptoms associated with fungal contact also include fungal infection, irritant reaction to spores or fungal metabolites, and toxic reaction to mycotoxins, described in the report as follows:

-- Infection: Most common indoor fungi grow near room temperature and do not easily grow inside the human body. Aspergillus is the most likely to cause respiratory infections, where most other fungi tend to infect the skin, nails and other areas of the body that function a lower temperatures.

-- Irritant: An irritant reaction to fungi exposure causes inflammation and can happen without previous hypersensitivity. Substances produced by fungi that are suspected to cause irritant reactions include microbially derived volatile organic compounds (MVOCs), ergosterols and glucans. MVOCs are produced by fungi as a byproduct of their metabolism, and their health effects are undetermined. They may cause nontoxic adverse effects as irritants or trigger psychological effects because of their odor. Toxic reactions do not likely occur as a result of MVOC exposure due to the low concentrations present in even the most contaminated environments.

-- Toxic reaction: Most toxic reactions to fungi occur as a result of eating mold-contaminated foods. A toxic reaction is unlikely to occur from inhalation of fungi since the amount of exposure generally is too low to cause health effects.

Indoor levels of airborne fungi are generally below outdoor levels of similar species in a well-constructed home without water damage. There can be some contribution from indoor sources, such as plants, pets and mold contaminates brought in on footwear and clothing.

“The best known management of indoor fungal contamination is prevention,” Dr. Portnoy said. “Regular inspection for sources of moisture and their elimination is the most important strategy to control indoor fungal growth. Since fungal growth depends on moisture and a carbon source, the most important strategy for reducing or eliminating its growth is controlling the amount of moisture present.”

Although the presence of damp conditions and carpets increases spore counts – forced air-heating systems, dehumidifiers, air filters, and air conditioners reduces them. The authors suggest the following additional steps to prevent mold growth: maintain indoor relative humidity at no greater than 50 percent; seal all leaks to prevent water accumulation and use a sump pump in basements prone to flooding; and increase the use of bathroom and kitchen ventilation by using exhaust fans.

“An individual should not panic at the first sight of mold growing in their home,” said Dr. Portnoy. “Small areas of visible mold growth should be cleaned with a dilute bleach/detergent solution, which kills viable colonies and removes fungal allergens. Commercial products are available for this purpose,” said Dr. Portnoy.

Patient information on allergic diseases is available by calling the ACAAI toll free number at (800) 842-7777 or visiting its Web site at http://www.acaai.org.

The ACAAI is a professional medical organization comprising nearly 5,000 qualified allergists-immunologists and related health care professionals. The College is dedicated to the clinical practice of allergy, asthma and immunology through education and research to promote the highest quality of patient care.

Citation: Portnoy, JM, et al. Health effects of indoor fungi. Ann Allergy Asthma Immunol 2005;94:313-320.

This study was supported in part by a grant from the Clorox Corporation.