Speaking from experience (not allergies, but tooth root problems), sneezing that is consistent means there may be an active infection. Sneezing that comes and goes… maybe, but it’s less likely. Over time, you just learn to recognize the difference between “normal” sneezing and possible URI sneezing. Of course, this is assuming that a vet has confirmed the cause of the sneezing. Since, you know, the default explanation is a URI.

The process is, unfortunately, elimination. There isn’t much you can do to prove allergies except change things within the environment. But you could have head x-rays done to rule out tooth root problems.

I forgot, does Charlie have a smooshed face? That dwarfism gene can squish a lot of structures within the skull, even putting kinks in “tubes” that drain the ears and eyes. This, itself, can cause chronic problems too.

Tooth root issues can come from age and poor dental habits, but it can also be from unlucky genes that tell the teeth to grow in odd ways.

I only have experience with URI, and when I hear thick, white discharge, my mind tends to stick to that. I know in humans, allergy-related nasal discharge can be yellow, green, or clear, so it might probably be that way for rabbits too. My only thought is, if it is a URI, treatment went on long enough to get rid of the large majority of the infection, and it is now at a level that your rabbit’s immune system is better actively combatting it, leading to less symptoms. In terms of timeline, your rabbit’s system may keep it at bay with the current symptoms or eventually the infection will get worse and treatment restarted. I always like to mention that my Wick’s URI (which we also considered, well maybe it’s just an allergy, due to its stubbornness) took several months of medication changes and adherence total to treat. Wick was literally medicated daily the entire time. From this experience, I’m biased to say that treatment wasn’t long enough or the medication (combo) was not optimal.

As LBJ10 mentions, allergy is a diagnosis of elimination, so you can see if changes in your environment relieve the ongoing symptoms you’re currently seeing.

Nasal discharges can definitely vary. I would notice thick white-ish discharge, even when the vet said there was no active infection. This was tooth root issues though, not allergies. I don’t know about allergies, but as Wick said, it could be possible.

If it were me, I would try a prolonged antibiotic treatment again. If that doesn’t work, then you could have some x-rays done to rule out tooth roots. If genetic, problems can begin at a young age. It’s usually around a year old, but I suppose it could happen even sooner. If it’s allergies, then that will be more difficult to pin down just because there are so many variables.