The appearance of the sputum, especially a change in color or consistency helps identify the cause. A yellowish, greenish, or brownish appearance may indicate a bacterial infection. Clear but very sticky (mucoid) sputum is characteristic of asthma. Bacteria and white blood cells are additional indications of infection. The presence of a specific type of white blood cell (eosinophil) suggests asthma. A cough may also produce blood, which commonly suggests bronchitis, but may also suggest more serious disorders.

It is important to consult a health care professional if there is a consistently dark, or blood like color, to your mucous.