Not all the molds are harmful, some are useful to human, and others are pathogenic, causing various illnesses to humans, animals and plants.
The biggest health problem from exposure to mold is allergy and asthma in susceptible people. There are more than 100,000 types of mold. Most people tolerate exposure to moderate levels of many different molds without any apparent adverse health effects.
Some molds produce highly toxic chemicals called “mycotoxins” that can produce illness in animals and humans especially if ingested. Scientific knowledge about the health effects of airborne mycotoxins on humans is quite limited.