Antimicrobials and the skin physiological and pathological flora.

Healthy human skin is regularly colonized by nonpathogenic microorganisms. Bacterial genera isolated are coagulase-negative staphylococci and diphtheroid rods on the skin surface and propionibacteria in the infundibulum of the sebaceous glands. As for fungi, Pityrosporum (Malassezia spp.) is regularly present. The distribution and density of the flora is dependent on age and environmental factors such as sebum secretion, occlusion, temperature and humidity. Odor production in the axilla is related to the activity of aerobic diphtheroids. Antimicrobials may reduce the density of the skin resident flora, but they do not completely eliminate it. While antimicrobials may cause irritant and allergic contact dermatitis, no evidence exists that the use of antimicrobial substances may change the ecology of resident bacteria on the skin thereby leading to the overgrowth of pathogenic bacteria.