I have been coughing up thick yellow phlegm and a headache for a week with no other symptoms. What can it be?
Just based on these symptoms, it is difficult to assess. This could be the latter presentation of a resolving respiratory tract infection. Remember that constant coughing may also cause a headache. You should see a doctor. If necessary, the sputum will be collected and sent to a lab for analysis. This article will provide more information on various causes of yellow sputum.