Runny nose can be caused by anything that irritates or inflames the nasal tissues. Infections — such as the common cold and influenza — allergies and various irritants may all cause a runny nose. Some people have a chronically runny nose for no apparent reason — a condition called nonallergic rhinitis or vasomotor rhinitis (VMR).
Less commonly, runny nose can be caused by polyps, a foreign body, a tumor or migraine-like headaches.
Causes shown here are commonly associated with this symptom. Work with your doctor or other health care professional for an accurate diagnosis.