What causes nosebleeds without injury?

There can be many causes of nosebleeds without injury. The main causes include dry air, allergies, nasal infections, sinusitis, high blood pressure, side effects of some medications, nasal polyps or tumors, vitamin C deficiency, or in some cases, hereditary diseases.

Some common causes of nosebleeds are:

Dry air: Dry air causes the skin inside the nose to dry out and crack, which can cause bleeding.
Allergies: Allergies can cause inflammation inside the nose, which makes the blood vessels sensitive.
Nasal infections: Sinusitis or other nasal infections can also cause nosebleeds.
High blood pressure: People with high blood pressure are more likely to have nosebleeds.
Side effects of some medications: Some medications, such as blood thinners, can cause nosebleeds.
Nasal polyps or tumors: Nosebleeds can also be caused by nasal polyps or tumors.
Vitamin C deficiency: Nosebleeds can also be caused by vitamin C deficiency.
Hereditary causes: In some cases, nosebleeds can also be caused by hereditary causes, such as hereditary hemorrhagic telangiectasia (HHT).

Other causes:

In some cases, nosebleeds can also be caused by nosebleeds or colds.

If you have frequent nosebleeds, you should consult your doctor.