Infections

This type of reaction from indoor mold is fairly rare, occurring primarily in those individuals who are susceptible. Aspergillus types of mold have been known to be pathogenic (a disease producing microorganism) For instance, Aspergillus fumigatus (A. fumigatus) is a fairly weak pathogen thought to cause infections in vulnerable individuals. A. fumigatus is also fairly commonly implicated in ABPA and allergic fungal sinusitis.

Other fungi that cause infection include Coccidioides, Histoplasma, and Blastomyces. However, these fungi are rarely found indoors, growing instead in soil and dirt. Human contact is usually due to contact with animals.
Many mycotoxins can produce changes or a weakening of the immune system.
Unfortunately, not all types or species of molds have been tested for the presence of mycotoxins. The production of toxins varies according to the type of mold, the substrate on which it grows, and seasons of the year.


Irritations

Fungal exposure can also come from any volatile compounds (VOCs) that a fungi/mold creates through primary or secondary metabolism that then becomes airborne. (Primary metabolic processes are those necessary to sustain the life of an organism.) These volatile compounds may be constantly created as the fungus consumes its food source during the primary metabolic process. VOCs can irritate the mucous membranes of the eyes and respiratory system.

Fungi that consume certain organic sources can release highly toxic gases. For instance, a fungus that grows on wallpaper often releases toxic gas arsine directly from the wallpaper that contains arsenic pigments. Thus, fungi and molds can release dangerous materials when they break down the host material. This can cause mucous membrane irritation in sensitized individuals.

Fungal volatile compounds may impact the "common chemical sense" which senses pungency and responds to it. This sense is primarily associated with the trigeminal nerve. The sensory and motor nerves respond to pungency by trying to hold the breath, discomfort, or through sensations such as itching, burning, and skin crawling. Changes in sensation, swelling of mucous membranes, constriction of respiratory smooth muscle, or dilation of surface blood vessels may be part of fight or flight reactions in response to trigeminal nerve stimulation. Reactions often include a reduced attention level, general disorientation, lowered reflex time, dizziness, etc.

Volatile Compounds found in or around homes can be responsible for mucous membrane irritants. It is thought that fungi can add to the already existing compounds when breaking down certain organic substances. A mold-contaminated building may have a significant contribution from its fungal contaminants that is added to common VOCs---building materials, paints, plastics and cleaners. VOCs in general can result in symptoms that include lowered attention span, headaches, lack of concentration, and dizziness.