Hi,
Has a chest xray and CT scan of your sinuses been done? Do you have any fever or sputum production?
Has a lung function test been done?
Have you had allergic reactions in the past? Are you allergic to any specific substances?
Do you have any other symptoms like breathlessness, reflux symptoms or heartburn or nasal symptoms like nasal discharge etc. Do you smoke?
Chronic cough is usually seen in cases of asthma, GERD or gastro esophageal reflux disease and sinusitis due to the post nasal drip.
You should try steam inhalation, warm saline gargles, saline nasal drops and oral antihistamine medications and see if it helps with your symptoms. If you have symptoms of reflux, you should try some antireflux, antinausea medications.
If the cough still persists, it would be best to consult your doctor and also get a chest xray done to rule out a chest infection.
Let us know about how you are doing and if you need any other information.
Regards.
maybe you have post nasal drip, have you seen an ent or anyone else. I know post nasal drips can cause thick mouscous should be clear and coughing to try and get rid of it.