Runny nose
A runny nose is excess fluid or mucus draining from the nostrils. It commonly accompanies infections, allergies, or irritation.
Nasal mucosa: The moist lining of the nasal cavity, containing mucus-producing cells, blood vessels, and immune defenses. Its glands and blood vessels produce and regulate the fluid that drains during a runny nose.
Common cold: A mild upper respiratory infection caused by various viruses, especially rhinoviruses. Viral inflammation commonly increases nasal secretions during a cold.
Antihistamine: A medicine that blocks histamine receptors and can reduce symptoms of allergic disease. Antihistamines can reduce allergy-related drainage, but may have little effect on a viral cold.
Nasal obstruction: Impaired airflow through the nose caused by narrowing or blockage of the nasal passages. Obstruction is a blocked-flow symptom; a runny nose is excess outward or backward drainage.
Chronic rhinosinusitis: Persistent inflammation of the nose and sinuses lasting at least 12 weeks, with characteristic symptoms. Long-lasting drainage with other symptoms may fit a chronic condition rather than a brief cold.
Mucus: A slippery secretion that traps particles and microbes and helps protect moist body surfaces. Changes in its amount and consistency shape nasal discharge.
Allergic rhinitis: Inflammation of the nasal lining caused by an allergic response to airborne substances. Allergic rhinitis often causes clear, watery drainage alongside sneezing and itching.
Nasal saline irrigation: Rinsing the nasal passages with sterile or appropriately prepared salt water. It can clear mucus and irritants without targeting a specific cause.
Epistaxis: Bleeding from the nose, commonly called a nosebleed. Blood from the nostrils is distinct from mucus or watery nasal discharge.
Unilateral nasal discharge: Nasal discharge that comes from only one nostril. One-sided, persistent, or unusual drainage can prompt evaluation for a localized cause.