Yellow discharge from the nose can be due to a nasal problem (fungal or bacterial infection, foreign body such as a piece of grass, nasal tumor), or to a draining toothroot abcess. Since the problem has persisted despite antibiotic treatment, further evaluation of the nose, sinuses and toothroots with xrays +/- CT scan is indicated. If xrays demonstrate a toothroot abcess, then extraction of the affected teeth would be needed. If a mass is found in the nose on xrays, then biopsy would be the next step.
Kimberly Coyner, DVM DACVD