I'd expect some noticeable improvement within maybe 72 hours. Complete resolution is harder to predict -- sinus infections sometimes get cleared in 10 days, like you'd expect for bronchitis or Strep or ear infections, but sometimes they take 14 or 21 days or even longer. The root term, after all, refers to an open space, so you have to get rid of the goo and not just permeate the tissue for long enough to kill the bugs.