The histological integrity of the nasal mucosa assures full efficacy of the respiratory, conditioning and defense functions. Together with ciliated and goblet cells, the respiratory epithelium not only carries out mucociliary clearance but it is also responsible for correct assembly of secretory IgA, the foundation of the mucosal defense system. The secretory component stabilizing the immunoglobulin molecule is indeed, an epithelial glycoprotein which begins to fail when the mucous trophism is altered through inflammatory processes of various natures. The efficacy of an anti-inflammatory drug (tiaprofenic acid) can thus be proven not only because the respiratory and mucociliary transport functions are normalized but, histologically speaking, through an accumulation of IgA in the epithelial cells and nasal secretions as well. In the present experiment the effect of tiaprofenic acid on the local production of antibodies appears prompt and long lasting. On the contrary, respiratory function and mucocillary transport are more deeply affected by structural alterations of the epithelium, most likely because the histological integrity-demonstrated by the increase of IgA in the secretion and accumulation of the secretory component in the epithelium-is the starting point for a perfect coordination according to fixed biological rhythms of all nasal functions.