Molds are classified into three groups according to human responses:
- Allergenic Molds: These don't usually produce life-threatening effects and are most problematic if you are allergic or asthmatic. The challenge is in figuring out what you are sensitive to. Children are particularly susceptible to mold allergies.
- Pathogenic Molds: These produce some sort of infection, which is of particular concern if your immune system is suppressed. They can cause hypersensitivity pneumonitis, an acute response resembling bacterial pneumonia. An example is Aspergillus fumigatus, which can grow in the lungs of immune-compromised individuals.
- Toxigenic Molds (aka "toxic molds"): These dangerous molds produce mycotoxins, which can have serious health effects on almost anyone. Possible reactions include immunosuppression and cancer. Mycotoxins are chemical toxins present within or on the surface of the mold spore, which you then unwittingly inhale, ingest, or touch. An example of this is aflatoxin, one of the most potent carcinogens known to mankind. Aflatoxin grows on peanuts and grains, and on some other foods.
- Alternaria: Commonly found in your nose, mouth, and upper respiratory tract; can cause allergic responses
- Aspergillus:4 Usually found in warm, extremely damp climates, and a common occupant of house dust; produces mycotoxins; can cause lung infections (aspergillosis5)
- Cladosporium: This very common outdoor fungus can find its way indoors to grow on textiles, wood and other damp, porous materials; triggers hay fever and asthma symptoms
- Penicillium: Very common species found on wallpaper, decaying fabrics, carpet, and fiberglass duct insulation; known for causing allergies and asthma; some species produce mycotoxins, one being the common antibiotic penicillin
- Stachybotrys:6 Extremely toxic "black mold" that produces mycotoxins that can cause serious breathing difficulties and bleeding of the lungs, among other health problems; thankfully, less common in homes than the other four, but not rare; found on wood or paper (cellulose products), but NOT on concrete, linoleum or tile