rabbit breathing hard (not been to the vet)

Question
Hello,
I am wondering whether you could help me.

I have a 5 year old dwarf rabbit, unaltered male.  I noticed since yesterday that he seems to be breathing harder than normal, with his nose moving more, and it sometimes looks his whole head is shakings.  It is similar to how he breathes when it gets hot, but I have had the central airconditioner on to keep it almost chilly(he lives in my living room, right next to the airconditioner vent), so it cannot be due to the heat right now.

He eats normally(he has been eating hay/greens/fresh banana/pellet food today), his pellet(poop) looks normal, and his temperature is 102.1, and he is not dehydrated (I pulled his skin to check).  

He doesn't have any discharge from his nose, nor from his eyes.  But in the past, he often had a runny eye (only on one side), which however hasn't come back for the past month.

Could you help me to figure out what ails him?  Could it be swollen nasal passage?  I read baby benadryl could help if that's the case, so I am wondering whether I should try it....  I have located a vet that is good with bunnies, but the office it quite far so I don't want to venture out in this warm afternoon, close to the rush hour....  I am thinking of taking him to the vet early morning tomorrow, but worried whether I should wait till then.  Thank you for your help!!!

Answer
Dear Jane,

If he's not in obvious distress and his temperature is normal, then you can probably wait until tomorrow to get him to the vet.  But I would not let this go for too long, as hard/labored breathing like this can signify pneumonia, even if there is no nasal discharge.  Chest radiographs are sometimes necessary to visualize the congestion in the lungs, as rabbits are very good at hiding signs of serious illness.  Sometimes even auscultation (listening with a stethoscope) doesn't reveal lung noise!

You can find an experienced rabbit vet here:

www.rabbit.org/vets

I hope he's fine, and that he's just too warm.  But if this is pneumonia and it's caught early, it is quite treatable with appropriate antibiotics.

Hope this helps.

Dana