Do you constantly have phlegm in your throat and don't know why? Here are some possible explanations.

3. Sinusitis

When the sinuses become inflamed, mucus may drain down the throat (postnasal drip).

This phenomenon may be accompanied by:

Nasal congestion,
facial pain,
headaches.
4. Changes in weather or dry air

Cold or very dry air can irritate the respiratory tract and stimulate mucus production.