The various forms of dermatophytosis, also called ringworm, are named according to the site involved. In general, anthropophilic species elicit little inflammation and cause chronic infections. Zoophilic and geophilic species, however, often provoke intense inflammation, which sometimes leads to eradication of the organisms and healing without treatment. Transmission may occur between humans by the sharing of combs, brushes, or headgear. Tinea capitis is caused only by Microsporum and Tricho phyton species.
Infection begins with invasion of the stratum corneum of the skin of the scalp.
In all three types of infection, scaling, hair loss, and inflammation of varying degrees are present. T. tonsurans, the major cause of tinea capitis in adults, characteristically produces a noninflammatory infection with either well-demarcated or irregular and diffuse areas of scaling and alopecia. Because the swollen hairs may fracture a few millimeters from the epidermis in this endothrix infection, the scalp sometimes appears to be marked by small black dots. Like all infections with Trichophyton species, these scalp lesions do not fluoresce under a Wood's light. Hair shedding late in the infection is common because the hair shaft is not damaged until the infection is well advanced.