Hydration alters viscosity of nasal secretions in postnasal drip

In our recent study, increased viscosity, delayed mucociliary clearance as well as hyposensitivity/dysesthesia of the nasopharynx seemed to play a relevant role in the pathophysiology of postnasal drip (PND) (1). Earlier concepts of PND, regarding an increased volume of secretions and atopy, do not seem to hold true since our latest analyses showed no significant difference between cases and controls (1). However, to this day its therapy is debated and the evidence for an effective treatment of PND is lacking so far. The fundamental rheological properties of nasal mucus constitute of the viscosity and elasticity (2-4). The viscosity of nasal secretions results from factors including the degree of hydration, pH, the electrolyte concentration, the quantity and types of mucins present, the presence of extracellular material, alterations in electrostatic interactions among mucins, as well as polymer length and degree of cross-linking (5).