A runny nose, medically known as rhinorrhea, is characterized by excess drainage produced by the nasal and adjacent tissues and blood vessels in the nose.1 This drainage can range from a clear, thin fluid to thick mucus.
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Here's a breakdown of what that means:
- Excess Mucus Production: The lining of your nasal passages and sinuses constantly produces mucus to keep the airways moist, trap dust and pathogens, and fight infection.
- Trigger: When something irritates or inflames the nasal tissues (like a virus, allergen, or irritant), the mucus production increases significantly.2 Blood vessels in the nose may also expand.3
- Discharge: This excess fluid and mucus then drains out of the nostrils (as a "runny nose") or down the back of the throat (known as postnasal drip).4
Common Causes:
- Infections: Common cold, flu, sinusitis.5
- Allergies: Hay fever (allergic rhinitis) triggered by pollen, dust mites, pet dander, etc.6
- Irritants: Smoke, strong odors, changes in weather (especially cold air), spicy foods.7
- Other Conditions: Crying, head trauma, deviated septum, hormonal changes, medication side effects.8
In essence, a runny nose is the body's way of flushing out irritants or pathogens from the nasal passages. While often annoying, it's usually a symptom of an underlying condition rather than a disease itself.9