The allergy skin prick test is kinda comical and you can't rule out all possible allergic hypersensitivity from that test alone. A skin prick test doesn't rule out food allergies (for instance). That test is very dependent on what was used in solution, in other words if they say "no reaction to dog dander" it doesn't mean you won't react to all breeds just whatever was used for that test. A negative skin histamine reaction doesn't rule out all environmental allergic reactions.
I've lived with Vasomotor rhinitis pretty much all my life (in my case it's simply allergy/genetic). If you believe it was a cold, you may have a bacteria or virus (which means antibiotics are useless) causing the problem, all you should/can do (besides riding it out), is eat well (more fruit and veg in your diet is never a bad thing, as silly as it sounds), get minimum 8 hours rest/night and manage the symptoms. I don't recommend going on nasal sprays long term.
Rhinocort, Beconase AQ, Fluonase, and Nasacort AQ are popular corticosteroids(and pricey) but you build up a resistance over time and they can be damaging to your mucosal membranes (long term).
Salt Water nasal rinses (also known as nasal irrigation) are very effective. Just google nasal irrigation or nasal rinse and you'll find out all you need to know.
One of my kids have throat polyps that has them clearing his throat all the time and makes him get hoarse very quickly if he overuses his voice. It's a genetic problem passed down from my Dad's side. Nasal and throat polyps are other possibilities and can cause hypersensitivities in the muscosa.
These kind of things are all very manageable (which may be good news especially since they're chronic).
My only beef with ent guys is that they pass you over very quickly. They stick a scope up your nose and make you stick out you tongue....see inflammation and quickly (very quickly) diagnose sinusitis or rhinitis, prescribe meds and send you on your way.
If you can find it (not likely though) ephedra is a fantastic natural decongestant. Another OTC solution to try is Reactine Allergy and Sinus (which has pseudoephedrine in it). I use the 12 hour instead of 24 hr stuff as for me, that works better and I can decide if I only need a half day dose or full strength.Your body can metabolize the 24hour stuff before you get a full 24 hours worth out of it (or so the pharmacist mentioned and my own personal experience has found that to be about right).
Good Luck.