Colorless sputum can be a non-specific sign of many lung diseases, most of them not cancer; a large number of them being due to infection, allergy, chronic
bronchitisAcute bronchitis
Bronchitis
Bronchitis and normal condition in tertiary bronchus
Cause of acute bronchitis
Cause of chronic bronchitis
Chronic bronchitis
Croup
Industrial bronchitis or a condition called bronchiectasis. It can also be a symptom of heart disease.
Although it is a non-specific sign, it is not one that can be ignored, without risking your health. You should see a doctor and have a chest x-ray done, without delay. There should also be a careful examination of your sputum, for bacteria and especially for tuberculosis (TB) and
atypicalAtypical pneumonia tuberculosis called nontuberculous mycobacterium (NTM) a
commonCommon cold 1 being mycobacterium avium complex (MAC). All in this group require special cultures and will not grow on a
routineRoutine sputum culture sputum culture.
You may have to see a lung specialist, also known as a pulmonologist, to work this out, but whatever you do, definitely seek medical help.