Fungi are living organisms naturally found on the body and in the environment. A decreased immune system can cause a fungal infection. According to the Centers for Disease Control, there are 1.5 million types of fungi in the world and 300 of those can make people sick.
Fungi live everywhere, in the soil, on plants and trees and even on human skin. Common diseases caused by a fungus are ringworm, fungal eye infections, candidiasis and histoplasmosis.
Fungi cause problems because they thrive in warm, moist environments and may enter the body through tiny cuts on the skin or when breathed in, according to the Mayo Clinic.
Humans have natural occurring bacteria on the skin. For the most part, the bacteria is harmless or even helps prevent infections.When a person has a lowered immune system due to illness, the good bacteria cannot fight off fungi or bad bacteria. Constantly being in damp conditions or sweating can also help the fungi grow. Fungal infections can also be spread from person to person. Washing hands and avoiding walking barefoot in damp areas can prevent the spread of any infections.