Brief Answer:
Oral antihistamine, lozenges like strepsil or cofsil

Detailed Answer:
Hi
Welcome
I have gone through your query.
I would like to know few more information like
Is there any history allergy?
Do you suffer from sinusitis? Sinusitis in the past?

Excess mucus causing coughing is likely related to post nasal drip of mucus.

This is a common condition. It can be due to allergies or an acute infection like cough and cold
If it has been occurring for a long time then allergies are more likely.

If you can determine the cause of the allergies and then eliminate or reduce your exposure to it , this would help
If could be to dust, pollen, animal dander, food or drink. This can be diagnosed by blood test or skin prick testing. See physician for examination. If require they may ask for chest x-ray to rule out bronchitis.

So I would suggest you to do steam inhalation with few drops of eucalyptus oil in it, few times a day -- helpful in case you have sinusitis.
Oral antihistamine like cetirizine at night for a week.
Use lozengs like strepsil or cofsil few times a day. These are better than halls.

if there is no improvement then yo may need medication such as montelukast or ketotifen which are used in persons who do not respond to typical allergy medicine.

Hope this helps
Take care

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