Why do dogs lick?

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As dog owners/guardians, we frequently observe our furry friends engaging in the universal dog behaviour: licking. But have you ever paused to ponder the multifaceted reasons behind this common canine behaviour? Why do dogs lick?

While licking is a regular occurrence, it arises from various motivations rooted deeply in dogs’ physiology, evolutionary history, and emotional states. For a quick overview, check the ‘Diagnostic differentials for licking’ table at the end of this article.

The origins…

From an evolutionary standpoint, it’s suggested that licking has deep roots going back to the domestic dog’s wild ancestors. Initially, puppy wolves would lick the faces of adult wolves to encourage regurgitation, an essential aspect of their feeding habits during their early stages (Serpell, 1995). It’s thought that this innate behaviour has carried over to pet dogs, explaining why puppies often lick their mothers, adult dogs, and their humans.

Functions of licking

Aside from its historical background, dogs maintain their hygiene through licking. It serves as part of their cleanliness routine as well as a mechanism to cool down, as the evaporation of saliva aids in reducing body temperature (Horowitz, 2017).

Licking also releases endorphins, which help provide dogs with a sense of comfort and pleasure. In addition, licking is also part of the dog’s greeting ritual, similar to shaking someone’s hand, so licking can help dogs build a bond with their caregivers (Bekoff, 2009).

However, licking isn’t just an affectionate gesture; it’s a tool for gathering information. Dogs have a heightened sense of taste and smell, which allows them to obtain detailed information about their environment and the individuals they interact with.

And, licking may also be used as a way to create space from another. For example, trainer Jennifer Shryock refers to this as a “kiss to dismiss”. For example, when the well-meaning visitor leans into the dog’s face, the dog may attempt to lick. The sight of a big, wet tongue looming towards them may cause the visitor to recoil and avoid getting slobbered with saliva. The space created by the person moving away can be rewarding to the dog, so the licking behaviour is repeated in similar contexts. This is a subtle cue to communicate a need for space or to end a less welcome engagement.

Some dogs lick because they have learned that it creates a strong, warm reaction from their handler, so the attention gained from their handler when the dog licks is highly rewarding. Hence, licking can be a learned behaviour for gaining attention; if your pet has realised that licking earns them affection/treats, etc., they might adopt this as a standard method to catch your attention (Herron et al., 2008).

In some instances, licking can be a manifestation of underlying anxiety, stress, and or pain/discomfort linked to various medical issues such as gastrointestinal and even hormonal imbalances. Therefore, dogs may resort to licking as a way to alleviate anxiety or any pain/discomfort (Landsberg et al., 2012). Engaging in this familiar activity provides a calming effect, helping them cope with environmental stressors (Dreschel and Granger, 2005). As pet carers, it’s crucial to be cognisant of the contexts in which licking occurs, and by observing your dog’s other body language signals that accompany licking, we can gain insights into the underlying emotions likely prompting this behaviour (Mariti et al., 2012). Understanding the different circumstances and cues can help distinguish between a lick borne of affection and one stemming from anxiety or another emotion, thereby enhancing the relationship between you and your dog through improved communication.

Further research supports this. Albuquerque et al. (2018) found that dogs were significantly more likely to lick their mouths when shown images of angry human faces, compared to happy or neutral expressions. The researchers suggest that mouth-licking in these contexts may signal appeasement or unease, offering further evidence that licking can reflect emotional processing. This underscores the importance of understanding how dogs perceive human emotions, rather than assuming their behaviour is solely driven by habit or affection.

It goes without saying that if you notice a sudden change in the frequency, intensity, or duration of your dog’s licking behaviour, then consult with your veterinarian.

Key take-aways

Whilst my grandmother’s answer for why dogs lick was always “They like the salt in your sweat,” this may fall under the categories of ‘fact finding’ and ‘taste’. However, we can see that there are many possible motivations for this behaviour. Through a patient and attentive approach, we can decode the language of licks, building a bridge of understanding and empathy with our four-legged friends.

References

• Albuquerque, A., Guo, K., Wilkinson, A., Resende, B & Mills, D.S. (2018) Mouth-licking by dogs as a response to emotional stimuli. Behavioural Processes, 146, 42-45. https://doi.org/10.1016/j.beproc.2017.11.006.
• Bekoff, M. (2009) The Emotional Lives of Animals. New World Library.
• Dreschel, N. A., & Granger, D. A. (2005) Physiological and behavioral reactivity to stress in thunderstorm-phobic dogs and their caregivers. Applied Animal Behaviour Science, 95(3-4), 153-168. https://doi.org/10.1016/j.applanim.2005.04.009.
• Herron, M. E., Shofer, F. S., & Reisner, I. R. (2008) Survey of the use and outcome of confrontational and non-confrontational training methods in client-owned dogs showing undesired behaviors. Applied Animal Behaviour Science, 117(1-2), 47-54. https://doi.org/10.1016/j.applanim.2008.12.011.
• Horowitz, A. (2017). Being a Dog: Following the Dog Into a World of Smell. Scribner.
• Landsberg, G. M., Hunthausen, W., & Ackerman, L. (2012) Behavior Problems of the Dog and Cat. Saunders.
• Mariti, C., Gazzano, A., Moore, J. L., Baragli, P., Chelli, L., & Sighieri, C. (2012) Perception of dogs’ stress by their owners. Journal of Veterinary Behavior, 7(4), 213-219. https://doi.org/10.1016/j.jveb.2011.09.004
• McGreevy, P., Georgevsky, D., Carrasco, J., Valenzuela, M., Duffy, D. L., & Serpell, J. A. (2015) Dog Behavior Co-Varies with Height, Bodyweight and Skull Shape. PLOS ONE, 10(12), e0149403. https://doi.org/10.1371/journal.pone.0080529
• Serpell, J. (1995). The Domestic Dog: Its Evolution, Behaviour, and Interactions with People. Cambridge University Press.
• Shylock, J. (2021). Kiss to Dismiss. Family Paws.

Quick overview – Example diagnostic differentials for licking

Differential Diagnosis	Description	References
Behavioural issue	Dogs may develop a habit of licking as a self-soothing behaviour, to appease, often stemming from anxiety and/or stress, boredom, frustration, and other factors.	[1]
Allergies	Dogs with allergies may lick themselves excessively in an attempt to relieve itching and discomfort. This could be due to food allergies, environmental allergies, or contact allergies.	[2]
Parasites	Infestations with parasites such as fleas, ticks, or mites can cause irritation and lead to increased licking.	[3]
Dermatitis	Inflammatory skin conditions, including atopic dermatitis, can cause itching and discomfort, prompting dogs to lick the affected areas.	[4]
Pain or discomfort	Dogs may lick a specific area of their body to alleviate pain or discomfort, potentially signaling an underlying health issue such as arthritis or injury.	[5]
Gastrointestinal issues	Dogs experiencing nausea or gastrointestinal upset may lick excessively.	[6]
Dental issues	Dental problems such as gingivitis or tooth abscess can cause discomfort, leading to increased licking.	[7]
Hormonal imbalances	Conditions such as hypothyroidism can cause skin issues that lead to increased licking.	[8]
Fact finding	Dogs use their tongues to explore their environment and gather information, which includes licking various objects or surfaces.	[9]
Gain attention (e.g., licking handlers)	Dogs may lick humans or other animals to gain attention and foster social bonds. Licking is typically linked to ‘greetings’.	[10]
Allogrooming	Allogrooming refers to social grooming behaviour where dogs lick each other to strengthen social bonds and maintain hygiene.	[11]
Distance Increasing	Dogs might use licking behaviour as a way to increase distance, such as licking another individual to communicate a desire for space or to avoid conflict.	[12]

Table references:

1. Horwitz, D. F. (2009). Behavioral Problems of Dogs. In Veterinary Clinics of North America: Small Animal Practice (Vol. 38, Issue 5, pp. 1005-1027. Managing Pets with Behavior Problems: Realistic Expectations – ScienceDirect
2. Olivry, T., & Mueller, R. S. (2017). Critically appraised topic on adverse food reactions of companion animals (3): prevalence of cutaneous adverse food reactions in dogs and cats. BMC Veterinary Research, 13(1). https://doi.org/10.1186/s12917-019-1880-2
3. Dryden, M. W., & Rust, M. K. (1994). The cat flea: biology, ecology and control. Veterinary Parasitology, 52(1-2), 1-19. https://doi.org/10.1016/0304-4017(94)90031-0
4. Marsella, R., Olivry, T., & Carlotti, D. N. (2011). Current evidence of skin barrier dysfunction in human and canine atopic dermatitis. Veterinary Dermatology, 22(3), 239-248. https://doi.org/10.1111/j.1365-3164.2011.00967.x
5. Hielm-Björkman, A., Kuusela, E., Liman, A., Markkola, A., Saarto, E., Huttunen, P., … & Raekallio, M. (2003). Evaluation of methods for assessment of pain associated with chronic osteoarthritis in dogs. Journal of the American Veterinary Medical Association, 222(11), 1552-1558. https://doi.org/10.2460/javma.2003.222.1552
6. Simpson, K. W. (1998). Diseases of the stomach. In Textbook of Veterinary Internal Medicine (4th ed., Vol. 2, pp. 1332-1354). WB Saunders.
7. Harvey, C. E. (1998). Management of periodontal disease: understanding the options. Veterinary Clinics of North America: Small Animal Practice, 28(5), 1129-1147. https://doi: 10.1016/j.cvsm.2005.03.002
8. Panciera, D. L. (1994). Hypothyroidism in dogs: 66 cases (1987-1992). Journal of the American Veterinary Medical Association, 204(5), 761-767.
9. Wells, D. L. (2003). The influence of toys on the behaviour and welfare of kennelled dogs. Animal Welfare, 12(3), 341-351.
10. Kuhne, F., Hößler, J. C., & Struwe, R. (2014). Effects of human–dog familiarity on dogs’ behavioural responses to petting. Applied Animal Behaviour Science, 155, 22-29. https://doi.org/10.1016/j.applanim.2012.10.003
11. Pal, S. K. (2008). Maternal care in free-ranging dogs, Canis familiaris. Applied Animal Behaviour Science, 111(1-2), 45-61. https://doi.org/10.1016/j.applanim.2004.08.002.
12. Mariti, C., Gazzano, A., Moore, J. L., Baragli, P., Chelli, L., & Sighieri, C. (2012). Perception of dogs’ stress by their owners. Journal of Veterinary Behavior, 7(4), 213-219. https://doi.org/10.1016/j.jveb.2011.09.004