Dermatophytes are a common label for a group of three types of fungus that commonly causes skin disease in animals and humans. These anamorphic (asexual or imperfect fungi) genera are: Microsporum

Microsporum

Microsporum is a genus of fungi that causes tinea capitis, tinea corpus, ringworm, and other dermatophytoses. Microsporum forms both macroconidia and microconidia on short conidiophores...

, Epidermophyton

Epidermophyton

Epidermophyton is a genus of fungus causing superficial and cutaneous mycoses, including E. floccosum, a cause of tinea corporis , tinea cruris , tinea pedis , and onychomycosis or tinea unguium, a fungal infection of the nail bed.-External links:**...

and Trichophyton

Trichophyton

The fungus genus Trichophyton is characterized by the development of both smooth-walled macro- and microconidia. Macroconidia are mostly borne laterally directly on the hyphae or on short pedicels, and are thin- or thick-walled, clavate to fusiform, and range from 4 to 8 by 8 to 50 um in size....

. There are about 40 species in these three genera. Species capable of reproducing sexually belong in the teleomorphic genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Arthroderma, of the Ascomycota

Ascomycota

The Ascomycota are a Division/Phylum of the kingdom Fungi, and subkingdom Dikarya. Its members are commonly known as the Sac fungi. They are the largest phylum of Fungi, with over 64,000 species...

 (see Teleomorph, anamorph and holomorph

Teleomorph, anamorph and holomorph

The terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota.*Teleomorph: the sexual reproductive stage , typically a fruiting body....

 for more information on this type of fungal life cycle).

Dermatophytes cause infections of the skin, hair and nails due to their ability to obtain nutrients from keratin

Keratin

Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...

ized material.