What causes nail infections?

Nail infections are caused by microscopic organisms called fungi. Skin-to-skin contact with someone with athlete's foot or ringworm on their hands can spread the fungi. Another common way to get a fungal nail infection is by walking barefoot in a warm, moist environment, such as a pool deck or locker room. Warm, moist environments are ideal for these fungi. Sharing an infected nail clipper or towel can also cause a fungal nail infection. But you don’t necessarily catch it from someone. Having moist nails or wearing sweaty socks and shoes can cause it.

In most cases, fungi infect nails by getting into:

• A small cut around your nail
• Nail crack
• Finger (or toe) and nail separation
  As a result of the warm, moist environment under the nail, fungi can grow easily. If left untreated, the infection can spread to other nails and even to your skin.

Prevention, Diagnosis, and Treatment

Prevention

• Make sure your hands and feet are clean and dry.
• Keep your fingernails and toenails short and clean.
• In areas such as locker rooms and public showers, avoid walking barefoot.
• Don't share nail clippers with others.
• Choose a nail salon that is clean and licensed by your state's cosmetology board. The salon should sterilize its instruments (nail clippers, scissors, etc.) after each use, or you can bring your own. 

Diagnosis
An examination of the affected nail and a discussion of your symptoms may help your dermatologist diagnose a fungal nail infection. Alternatively, the dermatologist may examine a nail clipping under a microscope or send it to a laboratory for fungi detection.
 

Treatment
Without antifungal treatment, fungal nail infections are typically difficult to cure. Prescription antifungal pills are usually the best treatment for fungal nail infections. A doctor may remove the nail completely in severe cases. Infections can last from several months to a year.