Flonase serious side effects. Call your doctor at once if you have a serious side effect such as:

  • severe or ongoing nosebleeds
  • noisy breathing, runny nose, or crusting around your nostrils
  • redness, sores, or white patches in your mouth or throat
  • fever, chills, weakness, nausea, vomiting, flu symptoms
  • any wound that will not heal
  • blurred vision, eye pain, or seeing halos around lights