What Causes Productive Cough During Nights In A Child?

My daughter is 5 years old and has had major problems with night cough with mucus that causes her to throw up sometimes this cough lasts over a month. She has been to a lung specialist, an allergy specialist and their findings is Rhinitis. She takes flonase every morning with a dulera inhaler and then takes dulera at night with singulair. At first it seemed to be helping and now I am just giving up hope that she will ever get better. I also notice she grinds her teeth at night and didn t know if this is apart of the problem. The doctors keep telling me her lungs are clear all her vitals are good. She has been tested twice in the past two years for full allergy panels and nothing ever shows up even tested for peanut allergy it was negative twice but if she has it she breaks out instantly. Now I am starting to wonder if it is our house or if it is our dogs even though she has tested negative. I need some guidance in this don t know what to do and I am very concerned for her. Please help.