What happens if rabbits start sneezing and breathing heavily?

Upper respiratory infections called "snuffles" are common with pet rabbits.

Sneezing and nasal discharge especially if white and thickened indicate one of several bacterial infections. An anti bacterial medication can be given by a vet after confirming the cause.

A rabbit with pneumonia or lower respiratory infection will show symptoms of loud raspy breathing and often stretches its neck to attempt to get more oxygen in with each breath. A rabbit showing these signs is critically ill and needs to be taken to a small animal Veterinarian right away.

There are no home remedies that work well enough to ensure recovery.