How do you tell your partner you’re not comfortable with him or her kissing the dog on the mouth? And then you.
Be direct and firm with your partner.
Dog kisses on the mouth can be so laden with germs and bacteria that a good toothbrush and toothpaste with a mouthwash that contains antiseptic are required before the next human kiss.
Let him or her know that you cannot kiss the same mouth that just kissed a puppy or a dog on the mouth, because you are concerned about the transmission of unwanted viruses and germs.
You might say, “I know how much you love your dog, and that is a wonderful relationship to have with your pet. I am really concerned about you kissing the dog and then kissing me. I need you to respect my feelings about this.”
Add that you are not against petting the dog.