Outside-in

In dermatology probiotic microorganisms have primarily been used orally for the prophylaxis and treatment of atopic disorders. In contrast to the successes achieved for gastrointestinal disorders, positive effects for atopic dermatitis only have been found in a few studies. New insights could now fundamentally change the impact of probiotics on dermatology. Probiotics are - like microflora of the skin - non-pathogenic microbes, which do not induce inflammatory responses in the skin. Common pathways for probiotics, non-pathogenic microbes, and microflora are characterized, in order to facilitate their more effective therapeutic use. These microbes display a majority of their effects directly at the site of application and thereby induce natural defense mechanisms. However, promotion of immunological tolerance is just as important in producing positive effects. Tolerance of the resident flora on surface organs developed during evolution and the mechanisms of action are multifaceted. Therefore, the topical application of probiotics and non-pathogenic microbes for prophylaxis and therapy of overwhelming cutaneous pro-inflammatory immune reactions is very promising. Results of recent clinical trials already have demonstrated the efficacy of this new therapeutic concept.