Otitis externa: This is the most common cause of ear drainage, especially in young adults. It is an infection of the outer ear canal, often caused by bacterial or fungal pathogens, and can be triggered by trauma, excessive moisture, or allergies.

Middle ear infection (otitis media) with perforation: If the eardrum is perforated due to an infection, it can lead to drainage from the ear. This condition often follows an upper respiratory infection.
Eczema or psoriasis of the ear canal: Skin conditions like eczema or psoriasis can cause inflammation and drainage in the ear canal.
Foreign body in the ear: The presence of a foreign object in the ear can cause irritation, infection, and subsequent drainage.

Malignant otitis externa: Although rare, this condition is a severe infection that can spread to the skull base and is more common in diabetic or immunocompromised patients. It requires prompt and aggressive treatment.
Cerebrospinal fluid (CSF) leak: Trauma to the head can cause a leak of CSF through the ear, which is a serious condition requiring immediate medical attention.
Mastoiditis: An infection of the mastoid bone, which is located behind the ear. If not treated promptly, it can lead to serious complications, including abscess formation and spread of infection to other parts of the skull.

Cholesteatoma: A type of skin cyst that can occur in the middle ear, often as a result of repeated infections. It can cause destruction of the surrounding bone and tissue, leading to drainage and other complications.
Relapsing polychondritis: A rare autoimmune disorder that can cause inflammation and destruction of cartilage in various parts of the body, including the ears, leading to drainage and other ear symptoms.
Tuberculous otitis media: A rare form of tuberculosis that affects the middle ear, causing infection and drainage. It is more common in areas where tuberculosis is prevalent.