• During outbreaks of tinea capitis a physician must be able to distinguish between Microsporum audouini and M. canis. In dealing with vesicular eruptions at other times, it is also essential to distinguish between fungus infection and contact dermatitis. In each case the treatment is different.
Hairs, scrapings from nails, vesicle tops, exudates, and scales can be examined under the microscope in the office by suspending and staining in a mixture of potassium hydroxide and ink. Cultures of pathogenic fungi can be made on Sabouraud's medium, which is easily prepared and can be sterilized in bottles in a pressure cooker.
Only a fraction of the vesicular eruptions on feet are caused by fungi. Eruptions caused by contact irritants are likely to be aggravated by applying fungicides. The procedures suggested here are to aid in making accurate early diagnoses and are neither expensive nor time-consuming.
Robinson HM, Cohen MM, Robinson RCV, Bereston ES. SIMPLIFIED OFFICE PROCEDURES FOR MYCOLOGICAL DIAGNOSIS. JAMA. 1956;160(7):537–540. doi:10.1001/jama.1956.02960420017004