Different Types of Nail Fungus

Dermatophytes are fungi that grow on skin, hair and nails. Infections caused by these fungi are called tineas. The fungi generally are not dangerous unless the patient has a compromised immune system. Tinea unguium is a toenail infection.

Tinea Unguium

• Tinea unguium (also called onchyomycosis) occurs when dermatophyte fungi invade the nails and skin under the nails. It is most common in toenails, because the toes tend to perspire and receive less exposure to fresh air. That creates a humid environment, which promotes fungal growth. In rare instances, fingernails can become infected.
  Nail fungi are mildly contagious. The infection is contracted through exposure to spores or fungal fragments in places where people go barefoot.

Symptoms of Tinea Unguium

• Several nails may be affected for a long time, while other nails on the same foot remain fungus free. It is not possible to tell by examination what species of fungus causes a nail infection, because all nail dermatophytes produce similar symptoms. Infected nails turn brown or black and become distorted in shape. Growth of the fungus under the nails leads to nail thickening and the accumulation of a lighter colored powdery material.

Fungi that Infect Nails

• The most common dermatophytes that cause nail infection are species in the genus Trichophyton. These species are keratinophilic, meaning they are capable of invading keratinized tissues (skin, hair and nails) by using enzymes that specifically break down keratin and other proteins found in nails. The fungus cells are white and filamentous and produce spores in the infected region.

Topical Treatment of Nail Fungus

• Natural treatments, such as tea tree oil or vinegar, have the best chance of working if the infection is caught early. Otherwise, the fungus will establish itself too far under the nail for those treatments to reach it. Alternatively, topical medicines for treating athlete's foot can be applied, though they often fail for the same reason as natural treatments.

Oral Treatment of Nail Fungus

• The best treatments for nail fungi are the oral antifungal drugs griseofulvin, itraconazole, fluconazole and terbinafine. These medications enter the bloodstream and travel to the site of infection. The fungi can't hide from them. The infected portion of the nail is slowly replaced by new nail until the fungus is eliminated. These drugs are not recommended for people with liver or heart disease.
  Treatment can take from weeks to as long as a year, depending on how fast the nails grow. If the treatment is stopped too soon after the fungus appears to be eliminated, recurrence is common.
  Most insurance policies do not cover treatment of nail fungi, unless the patient has an underlying condition that may lead to deeper infection. Treatment has historically been expensive ($500-$1,000 per course), but the advent of generic brands is reducing the cost significantly.