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Medical Author:

Allison Harvey, MD, FACEP

Medical Editor:

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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In this Article

• What other conditions can be mistaken for fungal nails?
• What causes fungal nails, and what are some of the risk factors?
• Is nail fungus contagious?
• What are the symptoms and signs of fungal nails?
• How are fungal nails diagnosed?
• How is nail fungus treated?
• Are oral medications for nail fungus toxic?
• What about the cost of oral medications?
• How do you prevent fungal nails?
• What is the prognosis of fungal nails?
• Conclusion
• Patient Comments: Fungal Nails - Treatments
• Find a local Dermatologist in your town
• Fungal Nails Index

There are many species of fungi that can affect nails. By far the most common, however, is called Trichophyton rubrum. This type of fungus has a tendency to infect the skin (known as a dermatophyte) and manifests in the following specific ways.

• Starts at the ends of the nails and raises the nail up: This is called "distal subungal onychomycosis." It is the most common type of fungal infection of the nails (90%). It is more common in the toes than the fingers. Risk factors include older age, swimming, athlete's foot, psoriasis, diabetes, family members with the infection, or a suppressed immune system. It usually starts as a discolored area at a corner of the big toe and slowly spreads toward the cuticle. Eventually the toenails will become thickened and flaky. Sometimes, you can also see athlete's foot in between the toes or skin peeling on the sole of the foot.
• Starts at the base of the nail and raises the nail up: It is called "proximal subungal onychomycosis." This is the least common type of fungal nail (3%). It is similar to the distal type, but it starts at the cuticle (base of the nail) and slowly spreads toward the nail tip. This type almost always occurs in people with a damaged immune system.
• Yeast onychomycosis: This type is caused by a yeast called Candida and not by the Trichophyton fungus named above. It is more common in fingernails and may be the most common cause of fungal fingernails. Candida can cause yellow, brown, white, or thickened nails. Some people who have this infection also have yeast in their mouth or have a chronic paronychia (see above) that is also infected with yeast.