Sneezing and congested cat

[chilledteacher]

Need some advice, we rescued our ginger menace 5 years ago from a cat rescue. He had been there a while because he was "in a bit of a state" when he arrived according to the owner and had been on the streets a long time before arriving with them judging by his injuries and illnesses.
He's now 7 and not a day has gone by in that time where he hasn't had horrific sneezing fits and congestion. TMI but my walls are constantly covered in cat snot which is a horrible brown colour (I do wash it off obviously) and I think there must be pressure (like when we get sinusitis) because his eye weeps.
I've taken him to the vets on numerous occasions and he's been prescribed bisolvin and I get told it's just one of those things. The bisolvin isn't working, I'm guessing it's not an infection because seriously 5 years!! He never has a temperature when the vet checks.
Anyone experienced this or have any ideas? It bothers us more than him I think.

I have a Persian exactly like this. I don't think Bisolven really helps. She also keeps getting conjunctivitis. I suspect she had cat flu when she was younger and never really got over it. She was a breeding queen in a kitten farm. And I'm awful condition when rescued. She occasionally has antibiotics if it's really bad. But I've not found an answer yet. I can't bear hearing her snuffling. If she was a baby I'd suction her. (Human nurse).

I had a cat like this and it was a left over condition from her having had cat flu as a tiny kitten. She had some kind of powdered stuff occasionally that stopped it but as soon as she came off that it just started up again. As giving it to her was tricky, we stopped and she just continued to sneeze and snuffle.

There was nothing wrong with her that the vet could find, I think he described it as "rhinitis" caused by the cat flu.