Anterior
90% of nosebleeds
Occur in anterior septum (Kiesselbach plexus)
Can visualize with anterior rhinoscopy
Posterior
10% of nosebleeds
Occur from nasopalatine branch of sphenopalatine artery
Cannot visualize without endoscope
90% of nosebleeds
Occur in anterior septum (Kiesselbach plexus)
Can visualize with anterior rhinoscopy
10% of nosebleeds
Occur from nasopalatine branch of sphenopalatine artery
Cannot visualize without endoscope
Digital trauma (i.e. nose-picking)
Rhinosinusitis
Anticoagulant/antiplatelet use
Trauma
Neoplasia, juvenile nasopharyngeal angiofibroma
Dried mucus membranes
Hypertension (does not cause bleeding but prolongs existing bleeding)
Osler-Weber-Rendu (Hereditary hemorrhagic telangiectasia)
Light source
Nasal speculum
Suction
Airway equipment
Packing or constrictive devices
Epistaxis
Facial trauma
Syncope 
Coagulopathy
Syncope
Nasal tumor
Anaphylaxis
Juvenile Nasopharyngeal Angiofibroma 