When I began researching dog licking behaviour I did so keeping in mind those dogs that lick infrequently and what it might mean. While I have uncovered some pretty solid theories, I also came across information on excessive licking that indicate an underlying medical condition that should be corrected by your vet.  And so I suggest up front that if your dog licks excessively, consult a vet immediately.

In this article I will firstly look at natural licking behaviours and their probable cause. Then I will provide a brief mention of problem licking and its more serious causes.

Firstly licking patterns are observed in puppies from a very young age and are thought to go back to instinctual survival behavioural traits inherited by wolves.

Many of us have seen puppies licking things - inert objects, organic material as well as other dogs and humans. In the first part of this article I will explore the reasons behind dogs licking other dog’s faces. ‘Good’ licking moves through several identified stages in a dog’s life. Initially when dogs are very young all of the litter siblings will tend to lick each other as a mutual social bonding mechanism. It builds affection and mutual satisfaction (Ref 1). Not only is the licking and being licked likely to be pleasurable, it also helps clean those very hard to get places that the mother will not always have time to reach.

Cat’s are more flexible and wet their paws before stroking their own heads etc, but puppies often rely on other puppies to lick their backs, neck and face. At some stage this familiar gesture moves into a means of communication between dogs. With its own siblings it is essentially saying “see how friendly I am” and of course this message can be quickly communicated with other non related dogs to show that they are no threat. (ref 1)

A little later in a puppy’s life licking performs another vital function. Again from wolf origins, when the mother wolf returns from a successful hunt the puppies surround her and lick her face to initiate a regurgitation reflex. This reflex is strong in wolves and the licking of the face and lips causes the mother to bring up semi-digested food which can easily be eaten by the pups. While this reflex is suppressed in most domestic dog breeds, it can still be found amongst some ‘sharp faced’ breeds that have a similar facial appearance to wild canines and wolves.

As a juvenile or adult dog, licking of other dog’s faces serves yet another purpose. While puppies and adult dogs still use it as a friendly gesture, adult dogs in particular do it as a sign of respect to a more dominant dog. As an act of submission the licking dog will also often lower its body to make it appear smaller and the dog receiving the licking will stand tall and not reciprocate the lick.

These natural licking instincts suggest that when a dog licks a humans face, they may also be wishing to communicated either that they are friendly (they like you), are hungry (please feed me) or accept that you are the pack leader (showing submission). There in lies the trick of working out in each situation exactly what your canine is after.

It is also thought that some dogs lick as a substitute for puppy mouthing behaviour. (ref 2) That is puppies often nip and ‘mouth’ each other in play and to help soothe teething issues. Dog owners often discourage puppies from chewing on people and so a puppy (and later the dog) learns to lick the person or other things instead. In an effort to please the owners they will sometimes change the mouthing behaviour to licking their owner’s face. We personally have noticed with our dog when we verbally disciplined them as a puppy that they needed an outlet for their excited mouthing behaviour and altered this to excitedly chewing knots/ grooming the hair on their fore paw.

When a dog meets an owner, or an owner’s friend, the dog licking their face is often part of the dog friendly greeting gesture that also includes wagging their tail and pulling their lips back in a ‘smile’. (ref 2)

So while a dog’s licking of a face serves several purposes as discussed above, why they lick other human body parts (arms and legs etc) or other inanimate objects remains more of a mystery. Licking of themselves, other dogs or humans may be part of a grooming ritual, a standard greeting, or dominance/ submission communication. However licking human appendages is thought to be to gain some valuable salt into their diet.

Obviously a dog licking your legs after you have a shower is partly to gain water as well as another display of affection. The licking of inanimate objects is thought to be tied to their way of exploring the world. Lack of opposable thumbs means that dogs must use their mouth and tongue to discover a lot of information about their environment which they can then record into their memory.

EXCESSIVE LICKING

When licking becomes excessive dogs can’t concentrate on other natural behaviours. Owners can readily establish how much licking is excessive but licking can either take the form of licking themselves, licking owners or licking of any other surface or object.

When a dog excessively grooms itself it can often be due to an annoying odour or substance on their coat or skin, or an allergy issue. As you are probably aware, dogs will roll in almost anything smelly and then deal with the consequence later. Licking can also be caused by more threatening causes that may be required to be handled by a vet. Poodles and other breeds can often become hyper allergic to many things in their environment. Seasonally this is often certain varieties of grasses in which case an allergic reaction can manifest itself in a dog excessively licking certain ‘hot spots’ on their body. These are well defined regions such as on their rump or paws or scratching their ears.

In exceptional cases dogs are classes as ‘face scrubbers’ and will take any opportunity to slide their face along rough surfaces such as carpet or grass to alleviate an itch. If your dog has an environmental allergy such as this, a vet can recommend the preferred cause of action which can involve removing contact with the allergen, ‘prescribing’ pharmaceuticals or anti histamines or even taking a desensitisation course via a dog allergist.

Excessive licking or grooming caused by an allergen (grasses or dietary) can often be identified on light coloured dogs by dark hair patches where they have habitually licked. A chemical in their saliva stains the hair a dark colour which some people mistakenly think are part of the breeds colour markings.

Other common causes of licking can be caused by thorns or burrs entering a dog’s skin. Typically post spring and summer spear grass can easily insert itself in a dogs paws or any other part of the body (as they roll and play on grass). These spears can easily penetrate the skin and cause much discomfort to a dog. If they do not dislodge themselves they will need to be surgically removed by a vet and potentially a course of anti-biotic prescribed.

Excessive self licking may eventually manifest itself in what is known as ‘acral lick dermatitis’ which may require cortisone treatment to alleviate the itch and allow skin to heal. An itch caused by a foreign body or allergy can become so overpowering that even after the cause is removed the dog is psychologically conditioned to continue licking the area. If an open would manifests itself, cortisone may also need to be supplemented by physically barriers to a particular area such as a bandage or neck cone collar.

Extreme excessive licking

In researching this topic I found a very informative article on repetitive licking that can lead to many medical problems. Firstly it describes first order or annoyance licking of such things as a dogs tendancy to “licks floors, carpets, walls, furniture, its own lips, and even the owner's legs, hands, or arms.” (ref 3) This is said to become more than an annoyance when ingestion of fibers etc it can cause an intestinal blockage requiring surgery.

The article concentrates on the licking of surfaces in the environment, probable causes and when to seek vet advice. The first advice the article makes is to accurately define the behavior by both documenting it (time of day, frequency and actions) as well as video recording it.

Some common causes can be related to anxiety, lack of interaction with other dogs and humans, lack of exercise or frightening interactions, changes in owner’s schedules.

Another cause of excessive licking can be associated with a “dog's diet (type, amount, and frequency fed), treats, and table scraps and any medications or supplements the dog is receiving” (ref 3). Some types of food and “many oral medications, such as non-steroidal anti-inflammatory drugs, metronidazole, and griseofulvin, and oral antibiotics such as cephalosporins, penicillins, tetracycline, and erythromycin can lead to nausea” (ref 3) which can be a major cause of excessive licking.

Because of the thoroughness of the original article I will lastly include the following information table, but urge you to read the article in full, or go straight to your vet if your dog has excessive licking.

Differential diagnoses for excessive surface and object licking include:

• Diseases that cause nausea or gastrointestinal discomfort (e.g. liver disease, exocrine pancreatic insufficiency, inflammatory bowel disease, intestinal lymphosarcoma)
• Dental or oropharyngeal pain or discomfort
• Adrenal disorders (hypoadrenocorticism or hyperadrenocorticism may cause excessive licking because of nausea, electrolyte disturbances, or polyphagia)
• Appetitive behavior (possibly as a result of mild polyphagia)
• Primary central nervous system disturbances (e.g. hydrocephalus, brain neoplasia, partial motor seizures)
• Attention-seeking behavior
• Anxiety
• Conflict- or frustration-induced displacement behavior
• Compulsive disorders
• Canine cognitive dysfunction.

CONCLUSION

As can be seen, dogs lick for many reasons. Many of them are an important part of their communication and bonding mechanisms with you, their owner and other dogs. Other licking actions signal more serious medical conditions such as anxiety, allergies or foreign body intrusion.

I hope that I have helped solve some of the more common mysteries behind why your dog licks you or itself, however excessive licking in any matter is cause for concern and suggests that you should consult your vet clinic as soon as possible.

References

1   http://www.pets.ca/dogs/articles/dog-licking-why-dogs-lick/

2  http://www.seefido.com/html/why_do_dog_lick_people.htm

3 http://veterinarymedicine.dvm360.com/vetmed/article/articleDetail.jsp?id=506866

Article by Bruce Dwyer. If you wish to use any of this information please refer to the article as a reference and provide a live link to http://www.dogwalkersmelbourne.com.au