The only symptoms I have are the constant phlegm and partially blocked nose. I have suffered for as long as I can remember (I am 2

at least for the last 5-6 years. It drives me crazy sometimes and I feel that my Doctor/s (seen several at my practice) do not take it seriously because it is not life threatening.
I have tried a dairy free diet and a low acidic diet which have not improved the condition.
I have been on a nasal spray and one a day anti histamine for some time (I have used the steroid sprays in the past). I don’t things these help much, apart from in the hay fever season when it’s worse. I use a nettie pot but don’t find I get much relief from this.
I have seen an ENT specialist which said there was some inflammation of my nose lining but no pollops. I was then referred to see a nurse for the skin prick allergy test. According to this I am allergic to mould, grass and tree pollen. These allergies only cover some months of the year but I suffer with the symptoms all year round.
I contacted allergy UK who advised that I was entitled to see a dietician to help with food elimination to test for food intolerances. I went back to the Doctors and persuaded them to refer me to see a dietician. I met with her this week and she told me she had looked on the internet for information on food intolerances and didn’t find much. She said it might just be something I have to live with. She asked which group of foods I would like to try cutting out next (thought that was her job to advise me on this) and I suggested wheat. So I am on a low wheat diet (eating white bread instead of brown etc) for 1 month.
I know that there is a test for food intolerance available but there is not any evidence to suggest it is very accurate, and it is expensive. I have also read something about have a CT scan to check to nasal passages. Can you suggest where to do from here if the food elimination does not work?
I have read on the internet I can try a 5 day fast then add in various food groups. I don't know if I would manage that as I am an active person. I suppose a fast would tell me one and for all if the problem is related to food...