Anything that irritates the inside of the nose can cause a stuffy nose. Infections — such as colds, flu or sinusitis — and allergies often cause stuffy and runny noses. Irritants in the air, such as tobacco smoke, perfume, dust and car exhaust, also can cause these symptoms.

Some people have noses that are stuffy and run all the time without a known reason. This is called nonallergic rhinitis or vasomotor rhinitis.

A polyp, an object such as a small toy stuck in the nose, or a tumor might cause the nose to run from only one side. Sometimes migraine-like headaches can cause a runny nose.

Possible causes of nasal congestion include:

1. Acute sinusitis
2. Alcohol
3. Allergies
4. Chronic sinusitis
5. Churg-Strauss syndrome
6. Dry or cold air
7. Common cold
8. Decongestant nasal spray overuse
9. Deviated septum
10. Enlarged adenoids
11. Food, especially spicy dishes
12. Gastroesophageal reflux disease (GERD)
13. Granulomatosis with polyangiitis (a condition that causes inflammation of the blood vessels)
14. Hormonal changes
15. Influenza (flu)
16. Medications, such as those used to treat high blood pressure, erectile dysfunction, depression, seizures and other conditions
17. Nasal polyps
18. Nonallergic rhinitis
19. Object in the nose.
20. Pregnancy
21. Respiratory syncytial virus (RSV)
22. Sleep apnea — a condition in which breathing stops and starts many times during sleep
23. Thyroid disorders.
24. Tobacco smoke