Choose hairs that fluoresce under a Wood's lamp or, if none fluoresce, choose broken or scaly ones. Nails scrapings are obtained from the nail bed or from infected areas after the outer layers are discarded. The specimen is mounted in a small amount of potassium hydroxide or calcofluor white. The KOH slides are gently heated and allowed to clear for 30 to 60 minutes before examining on a light or phase contrast microscope. Calcofluor white slides are examined on a fluorescent microscope.
Hyphae rounding up into arthroconidia are diagnostic of dermatophyte involvement.
Without the presence of arthroconidia the elements could also be due to a non-dermatophyte agent of onycomycosis or a small segment of a contaminating organism. The use of antibiotics will inhibit the overgrowth of bacteria and incorporation of cycloheximide will prevent the overgrowth of the rapidly growing saprophytic fungi The cultures are incubated at 30 C and examined frequently for 4 weeks.