Damaged nails allow dermatophytes to enter and infect the nail bed. Over time, the overlying nail becomes thickened, discoloured and eventually crumbly. In addition, during the early stages there can be small flaky white patches and pits on the top of the nail. 

A positive diagnosis depends on a culture of nail clippings and subungual debris – powdery material under the infected nail – but this can take several weeks. A new immunoassay (biochemical test) called Dermatophyte Test Strip is now available to podiatrists that can give a diagnosis in five minutes. Often the diagnosis is based on clinical findings; long-standing fungal foot infection almost always leads to fungal nail infection.

If the apparent infection is causing no problems then no treatment is required. If the infected nails are causing discomfort or the patient has diabetes, peripheral arterial disease, psoriasis or is immunosuppressed, then topical treatment should be offered in the first instance. Treatment for fungal nail infection takes months rather than days.