It starts dogs' digestion. Saliva/mucus help break down food and other particles in the mouth. Dogs swallow everything.
Ancient Egyptian canines licked wounds to heal because they thought dog mucus had medicinal qualities. Only partly true.
Mucus also includes rabies, salmonella, and campylobacter, a diarrhea-causing bacterium.
These germs are hazardous if you're bitten by a dog or touch excrement. They may also transfer via saliva.
Dogs licking faeces spread parasites through their saliva. Allergies are another danger.