Long term problem may be due to a form of allergic rhinitis. A useful treatment is Flixonase nasal spray (there are other brands) which is a nasal spray which is used continually to supress the lining of the nose and so reduce mucus production. Although it may take a day or two for the effect to kick in.
Use of antihistamines may also be useful.
Decongestant tablets for a couple of days are good to clear the airways , although they do increase blood pressure.
Steam inhalations twice daily for several days has the effect of liquifing the mucus making it easier to clear.
Finally, there are some homeopathic alternatives out there if you wish something complementary.
Hope this answers your question.
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