Sinus cavities are very hard to treat with anything except direct application and contact ointments, washes, etc. Taking antibiotics is not the answer unless you apply antibiotic ointment directly to the cavity. Alternate fingers so you do not reinfect. We struggled most of my son's early years with infections, that lead to inner ear issues as the infections backed up and spread from his nose. He was prescribed dose after dose of oral antibiotics, nothing worked until an EENT physician told us how to apply directly to the nasal cavity. Only then did this end.