People often think a dog's mouth is cleaner than a human's mouth. According to Dr. Leni K. Kaplan of Cornell University College of Veterinary Medicine, the reason people believe this because when a dog licks a wound, it can remove debris and contamination, which sometimes expedites the healing process. However, the fact is a dog's mouth is riddled with bacteria, and coming in contact with contaminated saliva presents a risk of disease and infection. Follow BI Video: On Twitter