What Causes Constant Running Nose Along With Fever And Chills In A Child?

My son is having running nose for past 20 days, he has allergic rhinitis. We are giving him nasonex nasal spray . He got cough after we started nasonex, but we continue d to give spray daily as the running nose was severe. Now from past 2 days he is getting fever with chills.we did not use spray for past 2 days.But we are worried about the fever as the nasonex medicine leaflet mentions child s immunity goes down while using spray, any infections can be severe. Now he getting 103 f temperature, gave metal p 5ml but temperature starts increasing after 3 hours. Could you please let us know how frequently can we give metal p? Could you please let us know your suggestions on medicine to be taken. And any other suggestions for further care. My son age 5 years 6 months old, 15 kg weight Medical history He suffered from running nose for 2 years.d doctor told us it is allergic rhinitis He suffered from enlarged adenoids , we used nasonex spray for 2 months in may and June months on doctors suggestion.