Onychomycosis refers to a fungal infection of the toe nail or finger nail. It is estimated that 50 million Americans suffer from onychomycosis. Onychomycosis causes the nail to become thick, yellow, and brittle. The organisms that cause onychomycosis are usually fungus (90% of cases) or yeast (7% of cases.) The onset of onychomycosis typically follows trauma to the nail. The onset of onychomycosis occurs between the ages of 20 and 80 and is found equally in men and women.


  • Nail that thickens and becomes discolored

  • Separation of the nail from the underlying nail bed

  • Pain with direct pressure to the nail from shoes

  • Difficulty trimming nails.


onychomycosisIt is safe to say that 50% of folks over the age of 50 have some degree of onychomycosis. But this doesn't necessarily mean that onychomycosis is due to "old age." We can imply that over the courseOnychomycosis of our lifetimes we would have more opportunities to acquire a fungal infection of the nail. The reason that onychomycosis becomes more prevalent with age is due to accumulated trauma to the nail over time. Trauma makes the nail much more susceptible to onychomycosis. It's also reasonable to assume that folks in professions or social activities where they may abuse their feet would tend to have a higher rate of onychomycosis. An example of activities that may abuse the feet and nails would include a mechanic dropping tools on their feet, horses or cattle stepping on the toes or runners who constantly injure their nails. Trauma to the nail is a common precursor to onychomycosis. Trauma may be something abrupt or something as benign as a pair of ill-fitting shoes constantly rubbing on the nail.

Healthy fingernail and toenail is an elastic, transparent layer of keratin. It is surrounded on two sides by soft skin referred to as the periungual folds. The base of the nail is called the eponychium and the distal tip of the nail is called the hyponychium. Nail cells are created in a small envelope called the nail matrix.Anatomy_toe_nailAnatomy_toe_nail

The onset of a fungal infection is often referred to as distal subungual, beginning at the tip of the nail and progressing slowly, proximally under the body of the nail. Although a small percentage of fungal nail infections begin in the eponychium (base of the nail), the vast majority begin in the hyponychium (distal tip of the nail) and progress proximally. Growth of the fungus is very slow, taking months to years to infect the entire nail.

The onset of onychomycosis can vary but most cases begin slowly and progress into the nail over a period of months to years. The nail will thicken as the fungus continues to grow. The filaments of fungus take up space in the nail, causing it to swell. The nail can be yellow, white or even green-to-black. The nail also becomes chalky and flakey.

Causes and contributing factors

The onset of onychomycosis has very little to do with hygiene. But unknowingly, we can contribute to the growth of onychomycosis. The environment inside the shoe is dark, damp, and warm. This environment is wonderfully conducive to the growth of onychomycosis.

Differential diagnosis

The differential diagnosis for onychomycosis includes:


OnychomycosisPrevention is an important aspect of the treatment of onychomycosis. The single most important thing that you can do to protect the nail from onychomycosis is to protect the nail from injuries. A healthy nail acts as a protective barrier against fungal infections. Once the nail is injured, the door of susceptibility swings open, allowing entry of the fungus. Also, keep the feet dry. Keeping the feet dry will inhibit the ability of the fungus to thrive. Frequent changes of socks, the use of a powder such as baby powder, and rotating shoes so that they are worn only every other day can help tremendously.

Medications used to treat onychomycosis may be topical or oral. There are any number of effective topical medications available over the counter. Topical medications are most helpful in treating early infections and for maintaining clear nails. Topical medications do have a limited ability to penetrate the nail to reach all of the fungal elements. Topical medication inhibits the growth of onychomycosis allowing for faster growth of the nail. Remember, fungus doesn't take a day off. Compliance is a big issue when using topical antifungals.

Onychomycosis can reoccur if your shoes are not properly treated, therefore use a shoe disinfectant may help. Keeping the feet clean and dry is another important part of treating fungal infections of the skin and nail. The daily use of a drying solution will significantly decrease the ability of a fungal infection to thrive.

The newer generation of oral antifungals, including Sporanox and Lamisil have been received very well by the medical community. These medications are used in a burst for 2 months to treat onychomycosis. Patients with a historyfungus toe nail of liver disease should avoid the use of these medications due to their potential hepatotoxicity. The older generations of oral Rx antifungal medications, such as Fulvicin or Griseofulvin, have been used successfully for years and are making a comeback due to their economic value. Use of an oral and topical antifungal concomitantly is common. It's important to recognize that the use of a topical or oral antifungal may temporarily treat onychomycosis, but the literature does show that most cases of onychomycosis will recur without the daily use of a topical antifungal. Topical antifungals are commonly used on a prophylactic basis to inhibit the recurrence of onychomycosis.

Patients who use a topical or oral antifungal medication should realize that the medications may not restore the normal shape of the nail. In long-standing cases of onychomycosis, nails change in shape, becoming thick and separate from the underlying nail bed. Oral and topical antifungals cannot restore the shape of the nail or re-attach the nail to the nail bed.

When all else fails, the fungal toe nail can be permanently removed. A nail avulsion is an office-based procedure. Most patients return to their normal shoes in just a Band-Aid within 24hrs following surgery. The removal of the nail is permanent. The site once occupied by the nail heals with skin that can be painted with nail polish.

Which treatment choice is right for you? Consider the following two examples:

Case 1. Sandy is a 24-year-old hairdresser who has intimate, hands-on contact with her clients on a daily basis. She has developed a fungal infection in several of her finger nails. She is concerned that the fungal infection will have a direct impact on her livelihood and does not want to spread the infection to others. Sandy is a good candidate for oral antifungal therapy.

Case 2. Joe is a 62-year-old farmer and has a long history of injuries to his hands and feet. His last visit to the doctor showed signs of an increase in his liver enzyme studies, indicating an overall decrease in his liver function. Joe has developed onychomycosis in most of his toe nails. Joe may likely choose to permanently remove the nail.

Treatment Guidelines - patient guidelines for treatment of nail fungus.

When to contact your doctor

Questions regarding treatment of onychomycosis should be directed to your podiatrist.


References are pending.

Author(s) and date

Dr. Jeffrey OsterThis article was written by Myfootshop.com medical advisor Jeffrey A. Oster, DPM.

Competing Interests - None

Cite this article as: Oster, Jeffrey. Onychomycosis.  https://www.myfootshop.com/article/onychomycosis

Most recent article update: January 14, 2021.

Creative Commons License  Onychomycosis by Myfootshop.com is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License.

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