The simple answer to this is that a dermatophyte is a skin-loving fungus. Dermatophytes are fungi that are adapted to live in animal tissues that contain keratin-the protein found in skin, hair, nails, hooves, and horn. Keratin is a tough protective substance that gives these tissues their firm texture. Dermatophytes are capable of breaking down keratin to obtain nutrients.
The extent of fungal nail and skin infections is normally limited to tissues that are not technically alive. Nails, hair, and the top layers of our skin are continually replenished by more growth from beneath; however, these tissues don’t have a blood supply and antibodies can’t readily reach fungi that grow there. Any answer to the question ‘what is a dermatophyte,’ should include the limitation that skin loving fungi typically only grow on, and break down, dead skin cells. They do not spread to other areas of the body unless the immune system is compromised.
The textbook answer to ‘what is a dermatophyte’ also excludes a number of other fungi that are sometimes implicated in fungal nail and skin infections. Most of these are environmental species that normally live on decaying organic material-compost, leaf litter, humus, animal remains etc.-and only rarely make the jump to living things. It’s generally agreed that these fungi can cause onychomycosis (fungal nail infections) but don’t invade skin. Various species of yeast are candidates as well, but they, too, are well known only in nail infections.
What is a dermatophyte? Specifically, it’s a fungus belonging to one of three fungal genera: Trichophyton, Microsporum, and Epidermophyton. A number of species within each genera cause fungal nail and skin infections; however, not all species do so. To recap: while being uniquely capable of living on and breaking down the hair, skin, nails, hooves, and horns of living humans and animals, dermatophytes rarely invade other parts of the body except when there is a problem with the immune system.
