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Health Effects of Molds

A Summary of AAAAI Position Paper

JACI, 117(2) 326-333. Feb. 2006,  Bush, Portnoy et al    

Molds are ubiquitous organisms that have been present for eons in man's environment. Indeed, our current evolutionary success stems in part from our ability resist infection and other adverse effects of molds. For the vast majority of people, molds are no more than an unsightly and malodorous nuisance. Recent suspicion that molds may be causing new types of illness have been circulating in the popular press.  Almost daily, claims of vague new symptoms and  illnesses  are ostensibly linked to molds without the rigors of the scientific process. Most of these claims do not withstand  scientific scrutiny of causality, or conform to known mechanisms of disease. In general,  difficulties  arise when any mold in the environment is implicated as the cause of multiple and different symptoms in different hosts. Most mold related illnesses cause a stereotyped response in susceptible individuals. While most of these illnesses do not have a provable connection to mold exposure, certain well defined illnesses are clearly linked to specific molds in  susceptible hosts.  Current medical knowledge  can correlate specific molds with specific disease states, but all affected individuals are afflicted in the same manner. In other words, molds cause characteristic illnesses by well defined mechanisms. These include:  

  • Allergy or immunologic hypersensitivity to a specific species of mold.
  • Direct infection, usually by a host with a weakened immune system.
  • Irritant effects of volatile mold by-products and vapors.
  • Mold Allergy and Hypersensitivity

  Mold allergy affects about 5% of the population. Mold-allergic people can be identified by a blood or skin test that measures IgE to specific molds. IgE  is an antibody produced  by people with allergies .It activates the immune system when the respiratory tract is exposed to minutes amounts of airborne allergen. There are at least two thousand species of mold, but about fifteen are responsible for most allergic symptoms. Considerable evidence links mold allergy as a trigger of asthma, but has been less conclusive for allergic nasal, eye and skin diseases.   One well defined syndrome occurring in persons with mold allergy or cystic fibrosis is called allergic bronchopulmonary aspergillosis. Affected individuals have asthma, antibodies of class IgE and IgG to the mold aspergillus fumigatus, and patchy densities in the lungs by chest radiograph. This illness usually responds to oral corticosteroids. Aspergillus, bipolaris and curvularia molds have also been found to cause allergic fugal sinusitis. Affected individuals have recalcitrant sinusitis, skin test reactivity to the previously mentioned molds and a special type of allergic mucous in their sinuses.   A different type of hypersensitivity reaction to molds results in a syndrome known as hypersensitivity pneumonitis. Repeated exposure to certain mold products triggers the cellular part of the immune system to attack the lungs. This is a much slower allergic reaction than the type caused by IgE. The inhaled substance can also be a protein of animal or vegetable origin. Therefore, it is most commonly occurs as an occupational disease, especially in farmers and bakery workers.  Repeated exposure to the mold of other foreign substance causes cough, fever and infiltrates on the chest radiograph. Clear diagnostic criteria exist and affected individuals have the same constellation of signs and symptoms.  

Mold Infections  

Infection with mold most commonly occurs on the surface of the skin or lining of the mouth or genital tract of women. Yeasts such as candida and other molds exist in low numbers in these areas, but multiply under certain conditions. These include excessive moisture, heat or sweating. This results in overgrowth  of yeast or mold and an irritating infection. Invasion of molds into the lungs, sinuses and even blood stream can be a serious infection and occurs in people with extremely weakened immune systems. A weakened immune system can be seen after cancer chemotherapy, HIV infection, organ transplantation, diabetes or debilitating disease. A few species of molds such as histoplasma, can cause lung infection in normal people if a large number of spores are inhaled.  

Irritant Effects of Molds  

Molds can produce potentially noxious and irritating substances that include spores, hyphae and volatile or airborne compounds. Even levels as  high as one million molds  spores/m3 have not produced symptoms in most people of inflamed eyes nose or lungs different from a controlled environment with much lower counts. Any irritating effects seen were short lived.  

Mold Toxins  

Certain mycotoxins, when ingested in large doses can cause specific illnesses. The source is usually contaminated hay and plant material fed to farm animals. These specific toxins, especially aflatoxins and ocratoxins are monitored in the food supply by law of the federal government. Farm workers are most commonly affected by mold toxins with a clearly defined constellation of signs and symptoms. Mycotoxins are usually adherent to other fungal particle and do not appear to become airborne in appreciable quantities. Therefore inhaling mycotoxins seems unlikely by the general population.   Immune system depression is theoretical concern as a mold related illness. The organ transplant rejection drug cyclosporin is a fungal toxin, but no cases of immunosuppression have been recorded in people with intense occupational mold exposure to molds.  


The mold stachybotrys produces a very potent mycotoxin, and has been suspected of causing a cluster of illness in Ohio. In this instance, an unexpected increase in cases of bleeding into the lungs occurred in a group of newborn infants. All the infants came from a housing development where the apartments  seemed to have water damage and mold infestation with stachybotrys. The CDC investigated this outbreak  and felt there was not enough evidence to incriminate the stachybotrys mycotoxin as the origin of the illness. Other mold researchers or mycologists have determined that stachybotrys only produces mycotoxins under periods of extremely high humidity. Under these conditions, where humidity levels are above 95%, the mycotoxin adheres to fungal particles and moisture prevents the particles from becoming airborne. Thus, the investigators were unable to explain how the toxins could become dispersed or airborne. In any event, if stachybotrys is causing a new illness, it is specifically lung hemorrhage in newborn infants. However, all the evidence thus far is to the contrary. Again if molds cause disease, it must satisfy the criteria of  specific symptoms, specific mold and specific host.  

Air Sampling for Mold  

This can be accomplished by several methods. The important point is that to prove significant indoor mold contamination exists, a simultaneous outdoor mold count must also be preformed. In many instances, it is found that the outdoor counts are appreciably higher than the indoor counts. Outdoor counts can approach hundreds of thousands of spores without the general public being aware or developing symptoms. But remember: specific mold, specific symptoms, specific illness and specific host.