I also had this disabling condition about two years ago.
During a series of flights I gradually felt more and more unwell- like I had the flu or something. On my last flight, I started to feel dizzy and was sick. If I moved my head it was worse.
When I finally managed to get home I couldn't get out of bed the next day. When standing, I fell. My GP diagnosed Labyrinthitis and was told to rest and it would probably go away in a week or two.
After two weeks off work I felt a lot better and my balance was normal again but I still had a fullness in my ear- like it was full of water. The GP referred me to a consultant ENT surgeon who examined me, checked my eye response to stimulus (turning my head) then did a full audiology examination and a pressure test of my ears (which showed that there was no fluid behind my eardrum). On these tests he said my labyrinthitis was better and cleared me for a return to work. For my first flight I was concerned about the pressure changes in my ear but I was fine. After a few days, the fullness in my ear cleared totally and I felt 100% again- luckily!
Some people are not so lucky though- some never get over the symptoms and have to live with a constant feeling of vertigo and this must be very debilitating. Obviously, this would be a bar to flying. Menieres disease has similar symptoms and this would obviously have to be investigated.
I found a lot of information on this website:
Labyrinthitis.org.uk - support for Labyrinthitis sufferers.