what causes fungus fingernails
Fungal Nail Infections-Cause. Fungal nail infections can be caused by three different types of fungus, alone or in combination. 1  Dermatophytes are a type of fungus that can grow on the skin, hair, and nails. 2  They don't invade the deeper tissues of the body.3  The most common dermatophyte, Trichophyton rubrum, causes most cases of athlete's foot. Dermatophytes cause almost all fungal toenail infections. 2  Yeasts are a type of fungus that grows on the skin and nails. 3  They are normally present on the human body. 4  Things like illness, antibiotic or birth control pill use, and immune system problems may allow an overgrowth of yeast, leading to a yeast infection.