Experts have advised against letting your pooch give you kisses as their mouths harbour all manner of germs.
They can also pass on fungal skin infections like ringworm and, in serious cases, can transmit toxocariasis, a parasite that can cause cysts to develop in the brain and the eyes, leading to blindness.
Professor Oxford told The Hippocratic Post that he would never let a dog lick his face.
"It is not just what is carried in saliva. Dogs spend half of their life with their noses in nasty corners or hovering over dog droppings so their muzzles are full of bacteria, viruses and germs of all sorts," he said.
Dr Helen Webberley, GP for Oxford Online Pharmacy, shares this view.
She told The Huffington Post UK: "Animals have different viruses, bacteria and parasites (worms) to humans and it makes very good sense to avoid any oral contact with animals to prevent the transmission of infections that we may not have the necessary immunity for.
"Some would say that you should wash your hands after any contact with animals, and although this may not be practical for the family pet, it should still be considered as good, preventative hygiene."
Salmonella and campylobacter are carried by dogs and passed on through their faeces. When another dog sniffs or (dare we say it) licks this faeces, it is transmitted to its muzzle.
Sadly, this bacteria could eventually end up on your face.
Campylobacter is the most common cause of food poisoning in the UK.
Common symptoms of a campylobacter infection include: diarrhoea, fever, nausea, vomiting, abdominal pain, headache and muscle pain. Salmonella can cause similar symptoms.
It is also possible for dogs to transmit fungal infections to humans. This occurs when someone touches a surface that has been in contact with the infection.
"These parasites can infect humans if they accidentally swallow eggs," Dr Hilary Longhurst, a consultant clinic immunologist based at St Bartholomew’s Hospital in London, told The Hippocratic Post.
She added that toxocariasis, a parasite that can cause blindness, is another dangerous health issue which could be potentially transmitted between humans and pets.
"It is particularly a risk for young children and adults who are immunosuppressed. If you take your dog to the vet every year to be de-wormed, this should help to reduce the risk of transmission," she added.