Everyone will have experienced the sensations caused by a viral (eg. common cold) or bacterial (eg. sinusitis) infection in the nose, or rarely a fungal (eg. Candida) infection, that results in the excessive production of thick sticky phlegm and mucus.
Hay fever and vasomotor rhinitis may swell the lining of the nostrils and produce so much watery mucus that they become blocked.
Polyps are quite common in the nose, and may enlarge to completely block one nostril. Other growths, such as tumours and cancers, may also do this, but are quite rare.
The nasal septum (mid line divider of the nose) may be pushed to one side and block a nostril due to a birth defect or a fracture of the nose.
The incidence of diphtheria in children is now low due to vaccination. It causes a sore throat, thick grey sticky membrane across the throat, fever, nasal discharge, hoarse voice and obvious illness, with overwhelming tiredness and muscle aches.
Numerous medications may have a blocked stuffy nose as a side effect. Significantly, most decongestant sprays that are used to clear blocked noses will actually make the blockage worse if used too often or for too long.