ABSTRACT
The stratum corneum is an excellent barrier to pathogenic microorganisms, but is itself sometimes the target of attack. The skin surface and its adnexal structures harbour a stable microflora, which lives in symbiosis with skin and may indeed be beneficial. Gram-positive cocci, Gram-positive lipophilic microaerophilic rods and a Gram-positive yeast-like organism live in the follicular lumina without normally causing much in the way of harm. Dermatophyte infections are restricted to the stratum corneum, the hair and the nails. Pityriasis versicolor disorder is caused by the yeast-like microorganism Pityrosporum ovale. This microaerophilic, lipophilic denizen of the normal follicle only occasionally becomes pathogenic when its growth is encouraged by heightened rates of sebum secretion or there is depressed immunity. Trichophyton, Microsporum and Epidermophyton species are responsible for this group of dermatophyte infections. Microsporum canis caught from dogs, cats or other children causes tinea capitis in children and, uncommonly, other types of ringworm infection.
