Runny Nose

Rhinorrhoea is the nasal lining doing its job too enthusiastically. Viral infection, allergen exposure, cold air, spicy food, or irritants all trigger glandular secretion and vascular leakage in the nasal mucosa. The colour of the discharge is a poor guide to cause: green mucus reflects neutrophil enzymes, not bacterial infection, and does not by itself justify antibiotics. The useful distinction is pattern. Viral rhinorrhoea starts clear, thickens over days, and resolves within seven to ten days, usually with sore throat and malaise. Allergic rhinitis is clear, watery, itchy, and comes with sneezing and eye symptoms, often seasonally or on exposure. Non-allergic (vasomotor) rhinitis has no itch and is triggered by temperature change, alcohol, or strong smells. Unilateral, persistent, blood-stained discharge is a different problem and needs examination. Rebound congestion from prolonged decongestant spray use — rhinitis medicamentosa — is a common self-inflicted cause of chronic symptoms and resolves only by stopping the spray.

• •Clear or thickened nasal discharge
• •Sneezing
• •Nasal congestion
• •Post-nasal drip and throat clearing
• •Itchy nose, eyes or palate (suggests allergy)
• •Reduced sense of smell

• •Viral upper respiratory infection
• •Allergic rhinitis (pollen, dust mite, pets)
• •Non-allergic vasomotor rhinitis
• •Irritants: smoke, perfume, cold air
• •Gustatory rhinitis from spicy food
• •Rhinitis medicamentosa from decongestant overuse
• •Nasal polyps or deviated septum

Mucosal inflammation increases both glandular output and vascular permeability. In allergy, IgE-mediated mast cell degranulation releases histamine and leukotrienes. In viral infection, cytokine release drives the same end result. In vasomotor rhinitis the mechanism is autonomic, with parasympathetic overactivity and no allergic component.