Skin is a major barrier against the environment and provides the first line of defense against invading microorganisms. Two papers in November 22 Nature and November 5 Nature Immunology show that cathelicidin and dermicin are antimicrobial proteins that enhance the protective response of the skin to a bacterial infection.

Victor Nizet and colleagues from University of California, San Diego, used a combined mammalian and bacterial genetic approach to analyze cathelicidins —proteins expressed on epithelial surfaces and in neutrophils. They found that cathelicidins are an important native component of innate host defense in mice and provide protection against necrotic skin infection caused by Group A Streptococcus (Nature 2001, 414:454-457).

In another paper, Birgit Schittek and colleagues from Eberhard-Karls-University Tübingen, Germany describe the isolation of the gene Dermcidin, which encodes an antimicrobial peptide having a broad spectrum of activity and no homology to other known antimicrobial peptides. This protein was specifically expressed in the sweat glands, secreted into the sweat and active in the high salt concentrations of the sweaty epidermal surface (Nat Immunol 2001, DOI: 10.1038/ni732).

These results suggest that the skin is not just a simple mechanical barrier but has an active antimicrobial activity immediately following bacterial colonization. In addition, sweat may be an important novel of life saving antibiotics.

Only one important question remains, is regular washing such a wise idea?