Differential Diagnosis for Clear Nasal Drainage from One Side

• Single Most Likely Diagnosis
  • Allergic rhinitis: This is often the most common cause of clear nasal discharge, especially if it's unilateral. Allergies to environmental factors like pollen, dust, or pet dander can lead to this symptom.
• Other Likely Diagnoses
  • Vasomotor rhinitis: This condition involves an overreaction of the nerves in the nose, leading to excessive nasal secretion. It can be triggered by various factors, including changes in temperature or humidity.
  • Anatomical obstruction (e.g., deviated septum, nasal polyps): Any physical blockage in the nasal passage can cause an increase in nasal discharge on the affected side as the body tries to clear the obstruction.
  • Infectious rhinitis (viral or bacterial): Although typically associated with purulent discharge, the early stages of an infection can present with clear nasal drainage.
• Do Not Miss Diagnoses
  • Cerebrospinal fluid (CSF) leak: Although rare, a CSF leak can present with clear nasal drainage, often from one side. This condition requires immediate medical attention due to the risk of meningitis.
  • Nasal foreign body: Especially in children, a foreign object lodged in the nasal passage can cause unilateral clear discharge.
• Rare Diagnoses
  • Fungal infections: Certain fungal infections can cause chronic nasal discharge, which may initially be clear.
  • Nasal tumors: Both benign and malignant tumors can lead to unilateral nasal discharge, among other symptoms.
  • Granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis): This is a rare autoimmune disorder that can affect the nasal passages and sinuses, leading to various symptoms, including nasal discharge.