Medical expert of the article
New publications
What causes a baby's runny nose?
Last reviewed: 04.07.2025
All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
The main causative agents of acute nasopharyngitis (runny nose) are viruses. These are primarily rhinoviruses (45% of all cases of the disease), less often - PC virus, ECHO viruses, coronaviruses, parainfluenza viruses and adenoviruses, as well as influenza B viruses.
Bacterial pathogens are less common, but still cause nasopharyngitis (runny nose). The most common of these are Mycoplasma pneumoniae, much less common is Chlamydoia pneumoniae, and even less common is Ch. psittaci.
Pathogenesis of acute nasopharyngitis
Acute nasopharyngitis (runny nose) is an acute inflammation of the mucous membrane of the nasal passages, as well as the mucous membrane and lymphoid elements of the posterior pharyngeal wall, accompanied by tissue edema and increased secretion of mucous secretions, or, conversely, increased dryness of the mucous membranes.