One day my kid brought a nasty flu from the kindergarten. My otolaryngologist recommended the strongest irrigation stream I can find to clean my sinuses.
Not only did it not help, but it also pushed some goo to the end of my sinuses, which resulted in pulsatile tinnitus.
After about 6 months my kid got sick again, so we all got sick, and I got rid of this tinnitus where I was hearing my heartbeat, by casually blowing my nose. The trick was having a stiff blockage, I guess, so the pressure builds up.
It sounds stupid and probably won't help you, but I wanted to share my story. I had no support from the people close to me and the heartbeat was driving me insane.
I'm sorry you have to go through this. Even though it's not a life-treating condition, it might be a life changing condition (QoL).
I have Tinnitus, which I first noticed when I was sick one time as a kid - probably 5-8 yrs old. Thankfully I have no other adverse experiences to report (related to this).
Anyway, I think I just have chronic inflammation.
It's not allergy either.