It doesn't take long, maybe 30 seconds or so, for me to get a good look inside your nose. One of the first things I notice is color. The color of your nasal membranes should be pink, the same color as healthy gums. If your nasal membranes are more red than pale and the discharge is thick and yellow, I'll suspect an infection. If your infection involves the nose, throat and ears and you have no fever or only a slight one, I'll suspect a cold virus.
Viruses often move around in the body.
Many patients will ask for an antibiotic when they have a cold, and I explain that antibiotics may work against bacteria but are powerless against a virus. For a viral infection in the nose, I'll usually prescribe decongestants to treat the symptoms. If you have a fever, with tenderness around the bridge of your nose and at the top of your cheeks, I'll suspect a bacterial infection that has invaded your sinuses. Usually, I can see dark yellow, thicker mucus draining from the sinus opening when bacteria are causing your illness. If I do suspect a bacterial infection, I'll prescribe an antibiotic.