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 do not invade the deeper tissues of
the body. The most common dermatophyte, Trichophyton rubrum, causes most cases of
athlete's foot infection, which 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 about 90% of fungal toenail
- Yeasts are a type of fungus that grows on
the skin and nails. They are normally present on the human body. Various
factors such as 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 are not usually passed between people.
Fungal infections are
classified by where they begin and what they affect.
Most fungal nail infections affect the skin under the nail (nail bed) and the
nail itself (nail plate).
Toenails are more likely to become
ingrown or injured, as from frequent nail trimming.
For more information, see the topic
A condition called
onycholysis, the separation of the nail from the skin beneath, can increase the
risk of fungal nail infections.
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 developing 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 do not take
It is not clear why some people are more
susceptible to fungal infections than other people.
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