Diagnosis of tinea

Note: Confirm diagnosis of tinea with microscopy and culture before starting oral antifungal therapy, or before starting topical antifungal therapy (if there is any doubt about diagnosis).

Confirm diagnosis of tinea with microscopy and cultures of skin scrapings, subungual debris, nail clippings or plucked hair:

  • before starting oral antifungal therapy
  • before starting topical antifungal therapy, if there is any doubt about diagnosis.

See also Indications for topical or oral therapy for tinea.

Microscopy and culture tests are simple and inexpensive; microscopy results should be available quickly, but fungal culture may take up to 6 weeks. Sometimes fungal culture (particularly from nail clippings) is negative, even after positive microscopy; this may be due to collection of insufficient specimen, recent use of antifungal drugs, or overgrowth of nonpathogenic species in the laboratory. If tinea is strongly suspected despite this negative culture, a trial of therapy is reasonable.

Tinea caused by the dog or cat ringworm (Microsporum canis) shows green fluorescence under an ultraviolet (UV) Wood lamp.