Nasal discharge and sputum are yellow, and this condition is mostly seen in infections or inflammations. After the respiratory tract is infected with these microorganisms, the body will secrete mucus or secretion to surround the mass of these microorganisms and prevent it from spreading. The mucus contains a large number of neutrophils, which will swallow up the bacteria, including viruses, that enter the body. When the phagocytosis reaches a certain level, the neutrophils will rupture by themselves and turn into pus when they break. When the pus is mixed with nasal discharge and phlegm, it will flow out. Therefore, if you see yellow nasal discharge and yellow sputum, which are symptoms of bacterial infection, you can use anti-inflammatory drugs, such as amoxicillin and cephalosporin.