More than 200000 different species exist but only about 200 cause human disease. They can be classified by shape and structure. In most the vegetative phase consists of filaments or hyphae which branch to form a mycelium or mould. Fungi can reproduce either sexually or asexually. Due to deposition of infected material directly onto the surface of skin, hair etc.
Organisms tend to be of low virulence.
They multiply within the superficial layers but usually remain confined to surface structures. Occasionally, the dermis may become involved with formation of a kerion, and sometimes the immune response to the fungus can be marked resulting in suppurating lesions. Diagnosis A skin scraping, nail clipping or piece of hair from an infected lesion is examined under a microscope after being soaked in potassium hydroxide to dissolve the keratin. Filamentous fungal elements can be seen and are diagnostic. Long-term steroids should be avoided.