Dogs can get bad breath (halitosis) for several reasons, including: 1. Poor Oral Hygiene & Dental Disease Plaque and tartar buildup can lead to gum disease, tooth decay, and infections, all of which cause foul-smelling breath. Gingivitis and periodontitis are common in dogs that don’t get regular teeth cleanings. 2. Diet & Eating Habits Eating smelly food or low-quality dog food can contribute to bad breath. Some dogs eat garbage, poop (coprophagia), or rotten food, which makes their breath even