When mold spores are present in large quantities, they can present a health hazard to humans, potentially causing allergic reactions and respiratory problems.

Some molds also produce mycotoxins that can pose serious health risks to humans and animals. Diseases may result from allergic sensitivity to mold spores, from the growth of pathogenic molds within the body or from the effects of ingested or inhaled toxic compounds (mycotoxins) produced by molds. Some studies claim that exposure to high levels of mycotoxins can lead to neurological problems and, in some cases, death. Prolonged exposure or daily home exposure may be particularly harmful. 

Symptoms caused by mold allergy include watery, itchy eyes; chronic cough; headaches or migraines; difficulty breathing; rashes; tiredness; sinus problems; nasal blockage, and frequent sneezing.