What Causes Sneezing And Coughing After Using Betnesol E/e/n Drops?

betnesol e/e/n drops recommended by hospital for treatment of nose polyps. Have been using these for approx 6 months, two drops each nostril twice a day. Recently am waking up sneezing and coughing continuously for about half an hour, but not after using drop in a morning. Why is this happening and is it still safe to keep taking these? If I stop the polyps are more than likely to return.