A runny nose is invariably due to excessive secretions from the nasal glands. It is a common feature of rhinitis and of nasal or sinus infections. Typically it is clear and watery. Thick yellow and green secretions are due to a bacterial or rarely fungal rhinosinusitis, as nasal infections commonly spread to the adjacent sinuses. Frequent nose blowing to clear the excess secretions may cause bleeding (epistaxis). Rarely a persistent watery discharge is due to brain fluid (cerebrospinal fluid – CSF) leaking into the nose and/or sinuses.