bacterial infection
"Have had sinus infections, at least twice a year, for over 24 years, Starts out as coughing & phlegm but within two days you can feel the difference between a regular cold & an infection in the chest area.  That's when what you cough up turns from clear, light green to thick tan/beige.  

Have had quite a few meds over the years, including Cleocin HCL 300 mg (this goes in a large Ocean Mist spray - works well). The doxycycline works the best but you MUST follow the directions.  One cap by mouth twice daily for ten days.  And TAKE WITH FOOD.  If you don't you will get the nausea & stomach upsets."