Suggest Treatment For Persistent Sinusitis And Coughing

Hi I have a 7 yr old daughter who suffers with sinusitis. I can t let her outside other wise she starts coughing and can t stop.its both distressing for both the child and I and I had her tested for allergies and she doesn t have any.when she gets really bad we end up on steroids and have had a stent in hospital over this too.when she wakes in the morning she always has black eyes and there quiet swollen and sneezes a lot. This is going on for 4 years.what can I do to help her