Your symptoms are related to your allergies. You most likely have a 'postnasal drip'. This means that phlegm drains from the sinuses and nose down the throat causing irritation. The usual treatment is the use of an antihistamine such as the one you are already taking. You will need to speak with your doctor about adding other medications such as a corticosteroid to control your symptoms since it seems that the antihistamine alone is ineffective.
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