The most common infection of the nail is caused by fungus. This is called onychomycosis. It is very common on the toenails and less common on the fingernails. About 40% of older adults have toenail fungus.
A sample may be taken from the affected nail and placed under the microscope and on a culture plate to identify the problem. Sometimes the nail appearance is classic for a fungus and the patient can be diagnosed clinically.
Topical antifungal creams and lacquers may be used but is difficult for them to penetrate the nail. These often keep the fungus from spreading but do not cure the infection. Oral medications like itraconazole and terbinafine may be used but may require blood test monitoring. These are usually necessary to try to cure the infection. Laser treatment of the nails, in addition to the previous treatments may help increase cure rates. There is no one treatment that guarantees a cure and not everyone clears completely. Combining several treatment modalities often increases the rate of clearing and long term cure.