• This technique is most commonly used in diagnosing tinea
corporis or tinea pedis.
• Although a lower sensitivity is found with this diagnostic test
for tinea capitis, spores within hair shafts can be visualized in “black
• Samples should be collected from the advancing edge or margins
of skin lesions with the edge of a scalpel.
• In children, use the dull edge if they are moving or use
• The foman blade, a 2-sided, spatula-type instrument, is less
likely to cut the skin of a moving infant.
• Shavings of nails left in KOH for several hours may assist in
diagnosis of onychomycosis.
• KOH is used to digest the proteins, lipids, and epithelial debris
in the specimen.
• Gentle cleaning of the area to be tested with an alcohol wipe
before this examination may remove confusing oil drops and excess
debris from the slide.