Springwatch presenter Chris Packham believes dog saliva has antibacterial properties and health benefits, but not all experts agree – Professor John Oxford warns dogs' muzzles are full of bacteria, viruses and germs.
It is one of those questions that can split even the closest of friends: would you allow a dog to lick your face? Medical views on the matter differ considerably.
Professor Graham Roberts, honorary consultant paediatrician in paediatric allergy and respiratory medicine, is quoted in medical journal The Hippocratic Post as saying that babies raised in households with pets are significantly less likely to develop allergies than those who grow up in pet-free homes. He states: "If you are born into a household where there is a pet, you are less likely to be allergic."
Others, however, such as Professor John Oxford, emeritus professor of virology and bacteriology at Queen Mary University of London, are firmly against overly close contact with dogs. He points out: "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."
Yet for BBC Springwatch's Chris Packham, there is no argument to be had. Speaking on the Oh My Dog podcast, the naturalist told host Jack Dee: "When we cut our finger, what's the first thing we do? We lick it. And you lick it because there are bacterial fauna in your saliva which have antiseptic and healing properties."
Similarly, he suggests there is a health advantage to be derived from dogs' saliva: "In days of old, when they were having medieval battles and doing unspeakable things to one another with swords, there were a lot of wounded people and they would allow the camp dogs to come and lick their wounds. They discovered that if the dog was licking the wound... it would be less likely to get infected."
All domestic dogs ultimately descend from wolves, and Chris explains that while a modest amount of a dog's saliva can benefit us, wolves' saliva possesses even greater healing properties: "I've been licked by wolves, been kissed by wolves," he says, "and they have even cleaner, or bacteriologically richer, saliva than dogs." They have never received antibiotics or other medicines that might compromise their natural state, he explains.
Chris notes that when wolves lick one another, it is part of ensuring the pack's survival: "When wolves go back to their den, in order to carry the food which they may have caught many kilometres away, they eat it and swallow it, and partially digest it. So when they get back to the den, the pups lick their lips and that stimulates the adult wolves to regurgitate the food."
"Now obviously," Chris continues, "dogs have lost that habit – they don't regurgitate for their young. But that licking is retained into adulthood in dogs because it's a greeting." In a similar vein, he explains that when dogs consume one another's excrement, there is a legitimate explanation for it. While this may appear revolting to us — lending weight to those who oppose face-licking — this behaviour also traces back to wolf instincts.
"Research has been done recently in California," Chris explains, "which shows that they will only eat faeces that are between one and two or three days old." He adds: "It was a relic of wolf behaviour. Because adult wolves will come back and eat all of the faeces in the den area when they've got cubs... because it's a way of reducing parasite load because the eggs of those parasites are in the faeces, and they don't want their young to get them."
"So that apparently appalling behaviour, because everyone's nauseated by the fact that their dog eats other dogs' faeces, that comes from the wolf and it's about reducing parasites."
