Infections of healthy skin or mucous membranes are rare despite constant exposure to microbial colonization. Nonspecific and specific defense mechanisms correspond in the nose: the mucociliary clearance provides very effective mechanical cleaning. If this protection is insufficient, the nasal epithelium comes into close contact with microorganisms. This triggers the recently discovered production of the body's own specific antimicrobial peptides (AP). It seems that it is difficult for microorganisms to form enzyme-induced resistance to AP. This makes AP highly interesting for the development of new antibiotics. The observation that antimicrobial activity can be induced has also led to the hypothesis that natural substances may possibly stimulate endogenous AP production. If this line of defense also fails, the inflammatory cells migrate from the blood into the tissue and, with their capacity for phagocytosis, the enzymatic attack on bacteria can cause a cellular inflammatory reaction in the nasal mucous membrane.