Why Do Dogs Lick People?

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The relationship dogs share with people is unique and they are often referred to as “man’s best friend”. They are believed to be the first animals to be domesticated by man about 36,000 years ago, and have since co-evolved with man(1). They are commensally associated with man; performing various tasks for people like protecting, hunting, herding etc., in exchange for food and shelter. In the present day, however, they perform more complicated tasks by associating with, and assisting the police, military units and handicapped people, thus justifying their moniker.

One might wonder if, over the long period of association with people, dogs have lost most of their functional behavioural traits that their ancestors once possessed. To answer that we will have to look deeper into the most common behavioural trait of our canid companions, Licking.

Over millennia of domestication, present day dogs diverged from the grey wolf (1), which is known to live and hunt in packs. In a pack members lick each other to communicate a variety of sentiments.

Canids lick their pack members to convey a casual hello, and greet each other(2). Licking each other also signifies grooming among pack mates(3). Ancient canids and wild dogs ascertain their social status by licking. They lick their powerful pack members to demonstrate submissiveness(4). This sometimes grants them permission to feast on the hunt along with their superiors. Young pups urge their mothers to regurgitate their food by licking them, so that they can feed on it. As they lick, they also use their tongues as sensory apparatus, learning crucial information about their immediate environment. Apart from this, licking themselves and their pups masks their scent from prey(5).

So when a dog licks its human pal, it is not only accepting him/her as a member of the pack but also establishing him/her as the alpha of the pack(4). They are sometimes requesting for food as a weaker member and at the same time regarding you as a mother who would feed them, although not by regurgitating. By using their sensory probes and their ability to process and interpret scented molecules in human sweat, they can detect if you are stressed(4). Although there is seldom a need to mask themselves or you from prey, they lick to convey their instinctive need for hygiene(6).

Dogs Licking People: Is it good?

The answer is both Yes and No.

Why YES?

It’s good for dogs because,

  • Licking is a dog’s way of communicating with you. When your dog licks you, it is primarily communicating that its hungry or its water bowl is empty or that it’s time to defecate(7). It also conveys that it is accepting you, happy to see you, or is seeking approval from you(8).
  • Dogs show their affection towards people by licking them. A dog’s first experience in the world is being licked by its mother to help it breathe and to comfort it. So when they are licking people they are reminiscing fondly their first experience in the world and sharing with them(6).
  • Licking helps dogs relieve their stress. This act releases endorphins – naturally produced chemicals in the body which relieve stress and give a sensation of happiness(9).

It’s good for people because,

  • When properly trained, dogs can help people in dealing with Post-traumatic Stress Disorder (PTSD) by licking. When persons suffering from PTSD are licked by a dog, it provides tactile stimulation to them and brings them back to full awareness thus intervening with their agitated state of mind and preventing them from harming themselves in extreme situations(10).
  • In ancient Rome and Greece and in medieval Europe, dogs were encouraged to lick people’s wounds to induce healing(11). Present day science confirms that tactile stimulation from licking increases blood flow in the site of the wound and the lysozyme in a dog’s saliva helps rupture the cell walls of bacteria, that cause infection(12).

 Why NO?

  • Although a dog’s saliva has antibacterial properties, flora in its mouth depends on what it ate recently and it is a known fact that dogs lick garbage, eat raw meat etc(13)(14).
  • Despite the fact that most of the pathogens that are infectious to dogs are not pathogenic to man, several cases of zoonosis have been reported. An infected dog’s saliva can transmit diseases like rabies(15,16), respiratory ailments caused by Pasteurella multocida(17) , Salmonellosis(18)
 

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