Normal Flora of the Skin

The mixture of organisms regularly found at any human anatomical site is referred to as the normal flora. Populations of microbes – such as bacteria and yeasts – inhabit the skin and mucus surfaces and are the body=s first lines of defense against illness and injury.

Their health depends upon the delicate balance between our own cells and the millions of bacteria and other one-celled microbes. Their role forms part of normal, healthy human physiology, however if microbe numbers grow beyond their typical ranges (often due to a compromised immune system) or if microbes populate atypical areas of the body (such as through poor hygiene or injury), disease can result.

It has been calculated that the surface of a human adult is covered with approximately 2 square meters of skin. The density and composition of the normal flora of the skin varies with anatomical locale. The high moisture content of the axilla, groin, and areas between the toes supports the activity and growth of relatively high densities of bacterial cells, but the density of bacterial populations at most other sites is fairly low, generally in the hundreds or thousands per square cm.

The greatest influence on bacterial populations appears to be body location. For example, the bacteria under our arms are likely more similar to those under another person=s arm than they are to the bacteria on any other part of the body. Most bacteria on the skin are sequestered in sweat glands and while sweat is essentially odorless some bacteria may consume it and create by products which result in body odor. In fact the vast colonies of microbes that live on us – bacterial, viral and fungal – are mostly harmless and necessary for our own good health.   Read more…