What Causes Fullness In The Ears And Vertigo?
Consider taking an antihistamine.
Detailed Answer:
Hello Mr. XXXX,
The eustachian tube connects the throat with the middle ear. When there is drainage down the throat and when people blow their nose, fluid can back up into the ear. This can explain the muffled hearing and the crackling or popping. There is likely some fluid, and increased pressure in the middle ear. Not everyone gets the vertiginous symptoms you described with it, but it is possible.
So basically the problem is that fluid is getting trapped (temporarily) in the middle ear.
The reason swabbing your ear won't show anything is because the fluid is behind the ear drum rather than in the auditory (ear) canal.
Here is a diagram of the ear and eustachian tube that might help: https://s-media-cache-ak0.pinimg.com/564x/96/71/23/0000b10bcd6d16ab1c6911d1e.jpg
Some people find that decongestants help, such as pseudoephedrine. If the primary problem is due to allergies, a good antihistamine such as Zyrtec (generic ceterizine) might help stop the problem at it's source. You can also try a nasal steroid such as Flonase - know that it will take a few days of daily use for the Flonase to start working.
I hope this information helps. Please let me know if I can provide further information.