Hi.
Noted history about suffering from severe
allergic rhinitis for last 12 years, black mucus filled in throat and salty cough, wants to know proper diet.
To answer your specific question about diet with the symptoms you have: you have to identify the foods, beverages, food products with preservatives that instigate or enhance the symptoms and stop these altogether. These are different for each person or patient.
Hence make a list of your own and do not listen to anyone else.
Now to discuss about your symptoms:
I think, you have to consult an ENT Surgeon for proper clinical evaluation, ENT
Endoscopy, and CT scan of sinuses.
Relevant tests of blood.
Vitamin D and A estimates.
Once a proper diagnosis is done and if there is no
diabetes then the best way is a 3 week course of tapering doses of
steroid, nasal steroid spray, rectification of
vitamin A and D if deficient.
This may clear all your problems.
Take care. Hope I have answered your question. Let me know if I can assist you further.
Regards,
Dr. T. Chandrakant, ENT & General Surgeon