I wonder if he is getting a urinary infection - feels like he has to "go" a lot?

Has he had a vet checkup lately?

I don't remember if you have tried this - but there is an antibiotic called zithromax that is supposed to be really good for 'snotty' kitties. Clavamox works well also(it is supposedly anti-viral).

Maybe just a very small dose of antihistamine would help Bobo. Time for a vet checkup here, just my opinion.