The lining of your nose contains many tiny blood vessels that lie close to the surface and are easily irritated.

The two most common causes of nosebleeds are:

1. Dry air — when your nasal membranes dry out, they're more susceptible to bleeding and infections
2. Nose picking

Other causes of nosebleeds include:

1. Acute sinusitis
2. Allergies — Injury, such as from a blunt trauma or burn.
3. Aspirin use
4. Bleeding disorders, such as hemophilia
5. Blood thinners (anticoagulants), such as warfarin and heparin
6. Chemical irritants, such as ammonia
7. Chronic sinusitis
8. Cocaine use
9. Common cold
10. Deviated septum
11. Object in the nose
12. Nasal sprays, such as those used to treat allergies, if used frequently
13. Nonallergic rhinitis
14. Trauma to the nose

Less common causes of nosebleeds include:

1. Alcohol use
2. Hereditary hemorrhagic telangiectasia
3. Immune thrombocytopenia (ITP)
4. Leukemia
5. Nasal and paranasal tumors
6. Nasal polyps
7. Nasal surgery

In general, nosebleeds are not a symptom or result of high blood pressure.