Nail fungus, or onychomycosis, is a condition that occurs when a microscopic fungus enters either a fingernail or toenail. It occurs in toenails more often than in fingernails.

Anyone can be affected by nail fungus, but infections are more common in people over the age of 60. For people who have diabetes or a weakened immune system, nail fungus can present serious risks.

Almost all fungal nail infections are caused by dermatophytes.

Four major types of fungal nail infection:

  • Distal subungual onychomycosis (DSO)
    • Most common type of fungal nail infection. It infects the skin under the end of the nail (nail bed) and in the nail starting at the end of the nail bed, and part of the nail often turns yellow or white. Pieces of skin and nail fragments build up under the nail. As the condition gets worse, the nail may crumble and split, and it may separate from the skin. A thickened nail and a large amount of debris under the nail may cause discomfort when wearing shoes. DSO can be a lifelong infection and hard to treat. Poor fitting cause may worsen or even cause the infection.
  • White superficial onychomycosis (WSO)
    • Second most common type of fungal nail infection which can be easily treated. It affects the top layer of the nail, first forming white spots on the nail surface. Eventually the entire surface of the nail becomes covered with a crumbly, chalky powder. The nail does not thicken and does not separate from the skin.
  • Candida onychomycosis
    • It is a yeast infection of the nail which is uncommon but can affect the nail and the skin bordering the nail (nail folds). It is more common in fingernails than toenails and may involve all of the nails at the same time and can cause the nail to separate from the nail bed. It invades weakened areas of the nail, which may become discolored white, green, or brownish, with an odd shape. The nail may look thicker than normal, and there may be signs of infection (reddened, swollen, tender, or warm) in the skin next to the nail (nail fold). Unlike the other types of fungal nail infections, the infection may be painful.
  • Proximal subungual onychomycosis (PSO)
    • It is more common in people infected with the human immunodeficiency virus (HIV). PSO infects the base of the nail (skin at the nail fold), often thickening the skin, which can separate from the nail. The base of the nail may appear white, and the nail opaque. The skin on top of the foot may become infected.

What Are the Symptoms of Nail Fungus?

  • Nail thickening and discoloration.
  • Pain in toes and fingertips may also occur.


Physician may do/request:

  • History & Physical Exam
    • Nail examination
  • Your doctor may scrape some tissue from under a nail and look at it under a microscope or send it to a lab to determine what kind of infection you have



  • Topical creams, gels, nail lacquers, or oral medications (antifungal drugs)
    • Oral drugs, such as terbinfine, can cure about 50% of nail fungus infections.
  • Rarely, surgery may be required. Although seldom done, removal of the infected nail can be performed to permit direct application of a topical antifungal.
  • Toenail infections are more difficult to treat than fingernail infections because the toenail grows more slowly. In addition, a damp, warm environment of a shoe or boot can encourage fungal growth.

Related Articles


Overview and FactsTypes and SymptomsDiagnosis & MedicationsOverview and Facts Referred pain is a phenomenon where pain is perceived at a [...]


Overview and FactsTypes and SymptomsDiagnosis & MedicationsOverview and Facts Quinoline yellow is a synthetic food colorant commonly used in the [...]


Overview and FactsTypes and SymptomsDiagnosis & MedicationsOverview and Facts Pneumothorax is a condition characterized by the presence of air in [...]