Nasal allergy(no specific cause)looking for long term solution ,have tried several treatments

Patient: Hi, I have a nasal allergy since childhood, but now it has increased .Also the allergic attacks occur all round the year. There is no definite substance to which i get allergic .When the allergic reaction begins i start sneezing and nose gets congested and and their is also nasal drip(This became a little more this year). I haven’t found any specific source of allergy during all these years , some times it starts when i wake up ( Although i get 8 hours sleep), sometimes it’s starts when smoke or strong scent is inhaled and at other times they cause nothing.I have seen several Specialists , most of them recommend nasal sprays (antihistamine or some other ) I have tried a whole lot of them but they don’t work pretty much(sometimes even make the allergy worse) , some recommended to use medicine ( contained montelocast sodium) the only medicine that works contains citrizine 2hcl , but it is a short term treatment only . I am really worried about the allergy as the intensity has increased in last few years. I also came to know of allergy shots but they are given only when their is a specific cause of the allergy but in my case their in’t any specific one.I am looking for a long term solution to it . Looking forward for your adviceRegards