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Nasal congestion

Catarrh is an excessive build-up of thick phlegm or mucus in an airway or cavity of the body.
Causes of catarrh
Catarrh is caused by the immune system reacting to an infection or irritation in an airway or a cavity of the body, such as inside the nose.
Diagnosing the causes of catarrh
In most cases, catarrh does not need to be diagnosed because the underlying infection will pass quickly, often without treatment.
Treating catarrh
Treatment for catarrh is not often necessary because it will disappear within a few days, after your body has fought off the infection.