Reasons for a runny nose
Viral infection: The most common cause of a runny nose is a cold. When the viruses that cause a cold spread to the sinuses, congestion occurs.
Allergies: Allergies to dust, pollen, pet dander, and perfumes cause increased mucus production in the sinuses and prevent it from draining.
Weather changes: Sudden cold, rain, or excessive humidity can affect the sinuses and cause a runny nose.
Structural obstructions in the sinuses: People with problems such as a deviated nasal septum and nasal polyps are more likely to have mucus trapped in their passages.
Smoking: Smoking damages the cells in the airways leading to the lungs and nose, increasing the risk of infection.
Dental problems: Infections in the upper teeth can sometimes spread to the sinuses.
