BACKGROUND: To determine the underlying mechanisms for rhinovirus-induced nasal secretions, nasal lavage fluids were analyzed during experimental rhinovirus infections. METHODS: Twenty patients with allergic rhinitis and 18 nonallergic control subjects were inoculated with rhinovirus type 39. Nasal lavage was performed before and on days 2 through 7 after viral inoculation, and the lavage fluids were assayed for proteins and mast cell mediators. RESULTS: The secretion of total protein and both plasma proteins (albumin and IgG) and glandular proteins (lactoferrin, lysozyme, and secretory IgA) increased after rhinovirus inoculation. Analysis of the specific protein constituents revealed that nasal secretions during the initial response to the rhinovirus infection were predominantly due to increased vascular permeability. Allergic subjects tended to have fewer symptoms and more vascular permeability than control subjects, and increased histamine secretion after rhinovirus inoculation was more frequently seen in the allergy group. CONCLUSION: Nasal secretions found early in the course of a viral upper respiratory infection are due to increased vascular permeability, whereas glandular secretions predominate later in the infection.