What is a runny nose?

Runny nose is the secretion of mucus from the nose. This can be caused by cold outdoor temperatures, the flu, or allergies. Another term you may see often is "rhinitis." Rhinitis is an inflammation of the nasal tissues. When a cold virus or an allergen such as pollen or dust first enters the body, it irritates the lining of the nose and sinuses, and the nose begins to secrete a lot of clear mucus. This mucus contains bacteria, viruses, or allergens and helps flush them out of the nose and sinuses. After two or three days, the mucus may change color and become white or yellow. Sometimes the mucus may also turn green. All this is normal and does not mean that there is an infection.

The breathing process begins in the nose. Air enters the lungs through the nose. The nose here helps filter, humidify, heat or cool the air that enters through it so that the air that reaches the lungs is clean and suitable.

A special lining of mucosa, or moist tissue, covers the area inside the nose and is made up of many mucus-producing glands. When bacteria, allergens, dust, or other harmful particles get into the nose, mucus traps them. Mucus contains antibodies or enzymes that kill unwanted bacteria and viruses. Also, the lining of the mucous membrane includes cilia, which are small hair-like structures. The cilia are constantly moving, moving harmful particles and mucus trapped in them through the nose to the back of the throat. They are then swallowed and destroyed by acid in the stomach.