Causes of nail infections include dermatophyte fungus, molds and yeast, according to Mayo Clinic. These fungi spread in moist and wet environments and are most likely to affect the toenails, reports MedicineNet.
Dermatophytes grow on hair, nails and skin and causes athlete's foot, according to WebMD. The athlete's foot may in turn affect the toenails. Individuals contract the infection when they come into contact with clothes, nail clippers, nail files and shoes that have dermatophytes.
Yeast is very common in the body, but factors such as taking antibiotics or birth control pills and certain illnesses may cause an overgrowth of yeast, explains WebMD. Yeast overgrowth may lead to yeast infection, which can affect the nails.
The fungi that cause nail infections thrive in warm and moist environments and easily spread from one person to another, according to WebMD. They are common in communal showers and locker rooms in gyms and in swimming pools, explains MedicineNet. Athletes get toenail infections a lot, presumably because they wear tight and sweaty shoes.
Individuals who are at risk of nail infections include people who have a weak immune system, diabetics and individuals who have diseases that affect their blood vessels, according to Healthline. The infections are more common in men than in women and in people who wear closed shoes such as boots and tennis shoes. The infections are also common in individuals who have nail injuries or who wear artificial nails.