From clear to black, here’s what your nasal discharge reveals about your health and when it’s time to see a doctor.

Allergies can cause white phlegm (mucus) or phlegm that has no color. Allergy treatment can include taking an antihistamine, using a nasal steroid, or consulting with an allergy specialist.

A runny or stuffy nose can be a symptom of the flu, a cold or allergies, and it can be hard to discern which one you have. So how do you know what’s really going on with your nose? “More than likely ...