Fungal nail infections can be caused by
three different types of
fungus, alone or in combination.
Dermatophytes are a type of fungus that
can grow on the skin, hair, and nails. They don't invade the deeper tissues of
the body. The most common dermatophyte, Trichophyton rubrum, causes most cases of
athlete's foot. Athlete's foot, in turn, can infect the
toenails. You can get infected by contact with objects that have dermatophytes
on them, such as clothing, shoes, nail clippers, nail files, shower and locker
room floors, and carpet. Dermatophytes cause almost all fungal toenail
Yeasts are a type of fungus that grows on
the skin and nails. They are normally present on the human body. Things like illness, antibiotic or birth control pill use, and
immune system problems may allow an overgrowth of
yeast, leading to a yeast infection.
Molds (often called nondermatophytes) are
a type of fungus that commonly grows in soil and can grow on the skin and
nails. They aren't usually passed between people.
You can get a fungal nail
infection when you come in contact with the fungus and it begins to grow on or
under your nail. Fungi grow best in warm, moist areas, such as the area around
the toes. But you can have fungi on your skin without getting a nail
infection. You have to be likely to get the infection (susceptible)
for it to develop. If you are susceptible to fungal infections, they tend to
return, even after successful treatment and especially if you don't take
It is not clear why some people are more
susceptible to fungal infections than other people.