Epistaxis (Nosebleed): This is the most common cause of passing blood clots through the nose. It can be caused by dry air, nose picking, trauma, or other factors that lead to the rupture of blood vessels in the nasal mucosa.

Allergic Rhinitis: Inflammation and irritation of the nasal passages due to allergies can lead to bleeding and the passage of blood clots.
Sinusitis: Infection or inflammation of the sinuses can cause bleeding and discharge, including blood clots, through the nose.
Nasal Polyps: Growths in the nasal passages can cause irritation, bleeding, and the passage of blood clots.
Hypertension: Uncontrolled high blood pressure can lead to epistaxis, including the passage of blood clots.

Nasal Tumors (Benign or Malignant): Although less common, tumors in the nasal cavity can cause bleeding and should not be missed due to their potential for serious complications.
Vascular Malformations: Abnormalities in blood vessel formation can lead to recurrent, severe nosebleeds, including the passage of blood clots.
Coagulopathy: Disorders that affect blood clotting, such as hemophilia or the use of anticoagulant medications, can lead to significant bleeding, including through the nose.
Invasive Fungal Sinusitis: A serious infection that can cause destruction of the nasal and sinus tissues, leading to bleeding and potentially life-threatening complications.

Wegener's Granulomatosis (Granulomatosis with Polyangiitis): A rare autoimmune disorder that can cause inflammation of the blood vessels, leading to bleeding and other symptoms.
Hereditary Hemorrhagic Telangiectasia (Osler-Weber-Rendu Syndrome): A genetic disorder characterized by the formation of abnormal blood vessels, which can lead to recurrent nosebleeds.
Nasal Foreign Body: Although more common in children, the presence of a foreign object in the nose can cause irritation, bleeding, and the passage of blood clots.