The majority of fungi does not have a negative effect on humans, although some species can cause disease. One example of this is indoor mold, which can cause and exacerbate respiratory conditions, according to the University of Minnesota.
Although the majority of fungi do not cause harm to humans, those that do can have severe effects. For example, if opportunistic fungi from soil enter the wound of a person whose immune system is compromised, such as a diabetes patient, it can cause an aggressive infection. The majority of infections fungi cause are superficial, which means they occur across the skin or the hair. Examples of this include athlete's foot and ringworm.
When fungi do enter the body as an infection, they can cause systemic reactions that are fatal. People who are living in households where mold is present are at risk of developing superficial and internal infections. The type of infection they encounter and how severe it is depends on the fungi type and how toxic it is. For example, people inhaling green mold are at higher risk than those inhaling other types. Health problems arising from mold inhalation include allergic reactions, sinusitis as a result of allergen exposure, pneumonitis and allergic asthma.