According to PetMD, the most common causes for sneezing in younger dogs include infections, excessive nasal secretions, mucus irritation and gastrointestinal issues. The most common causes for sneezing in older dogs are nasal tumors and dental issues. Chronic dental issues in dogs can lead to chronic sneezing.
Petplace.com explains that sneezing in dogs can occur for multiple reasons that range from brief conditions to viral infections. Seasonal allergies and blockages are also common culprits. Younger dogs are more prone to viruses, while older dogs tend to be more prone to chronic dental disease. Constant sneezing in dogs can also be caused by inhalation of foreign bodies.
According to WebMD, sneezing in dogs is an early sign of irritated nasal passages. While an occasional sneeze is considered normal behavior, constant sneezing can be the sign of a more serious condition, so it is important to consult with a veterinarian as soon as possible to ensure prompt diagnosis and treatment. Scented candles and perfumes can also irritate a dog's nasal passages and cause sneezing. Sudden bouts of sneezing that are accompanied by pawing at the nose often suggest a foreign body is caught inside the nasal passage. Chronic sneezing in dogs can lead to swollen and congested nasal membranes.