Why do dogs lick each others mouths?

Dogs licking each other’s mouths is an everyday gesture you might catch at the dog park, during a reunion at the front door, or when two dogs meet in the yard. It’s small but meaningful: the motion can tell you about the relationship between the dogs, where they sit in a social group, and sometimes whether something is wrong physically. Owners often notice it and feel reassured when it looks gentle — or alarmed when it seems obsessive or leads to a fight. Because the action ties back to puppyhood and mother–pup care, it can pull on an owner’s instincts in the same way, looking both nurturing and communicative at once.

At a glance — what mouth-licking between dogs actually means

When one dog licks another dog’s mouth, it may serve several overlapping purposes. Often it is a greeting or affiliative signal: a dog that approaches and licks another’s face is likely saying, in canine terms, “I come in peace.” It can also appear as an appeasement or submission behavior when a lower-ranking dog interacts with a higher-ranking partner. The movement has roots in maternal care — puppies lick a mother’s mouth when soliciting regurgitated food, and adult dogs sometimes show a residual feeding or grooming instinct that resurfaces in social contexts. Finally, mouth-licking transfers taste and scent information; dogs are sampling chemical cues from breath, saliva, and recent meals to update their social and environmental map.

Social signaling and biology: the instincts behind the behavior

In a social species, simple movements become signals through repetition and response. A mouth lick is one of those signals that is likely linked to both social hierarchy and relationship quality. In many encounters the licker is the less-dominant or more submissive partner; by approaching gently and offering a lick, that dog signals non-threat and solicits tolerance. However, dominance explanations don’t cover every case — long-term bonded pairs and close friends also exchange licks in relaxed contexts, which is why context matters.

The behavior has a clear maternal origin. Puppies lick their mother’s face to encourage regurgitation when they are very young, and mothers lick pups to clean and stimulate bodily functions. That early-life pairing of mouth contact with feeding and comfort may leave a lasting neural association so that adult dogs revert to similar gestures in affiliative or conciliatory contexts.

Beyond social coding, mouth-licking serves functional roles such as allo-grooming and hygiene. A dog may pick at food residue or parasites around another dog’s mouth; in doing so it also reinforces social bonds. Mouth and facial licking deliver chemosensory information, too — saliva and breath carry volatile compounds and pheromones that a dog’s vomeronasal organ and olfactory system are equipped to detect. What looks like an affectionate lick can be an efficient way for dogs to gather data about what the other dog has eaten, whether it is ill, and its emotional state.

Context matters: common triggers and situations that spark mouth-licking

• Greetings and reunions: Dogs commonly lick at the face shortly after meeting or when they meet again after being apart; the lick helps re-establish the relationship.
• Around food or novel smells: If one dog recently ate or encountered a new scent, others may inspect and lick that mouth to sample the information.
• After play or during calming sequences: Licks can occur during the cooldown phase after rough play, sometimes as part of a sequence that de-escalates arousal.
• Stressful situations: In some dogs, mouth-licking increases when they feel anxious; the motion may function as a self-calming gesture or as an appeasement signal toward a perceived threat.
• Age, breed, temperament differences: Puppies and young dogs typically engage more in mouth licking due to developmental and maternal carryover. Some breeds with strong social predispositions or high reactivity may show the behavior more often; individual temperament matters most.

Health risks and red flags — when mouth-licking signals a problem

Most mouth-licking is harmless, but several signs suggest the need for attention. Excessive or compulsive licking — where a dog repeatedly targets other dogs’ mouths beyond normal social exchanges — may suggest anxiety, an obsessive-compulsive tendency, or boredom-driven behavior that benefits from intervention.

If licking is accompanied by blood, swelling, bruising, persistent bad odor, or visible wounds, suspect injury or infection and act promptly. Dogs can damage lips, teeth, or surrounding tissue during an aggressive interaction that begins as a mouth investigation. Sudden changes — a dog that used to accept licks but now snaps, growls, or stiffens — may indicate pain in the recipient, dental disease, or an underlying illness that makes contact uncomfortable.

Pathogen transmission is a practical concern in certain contexts. While casual licking between healthy dogs is usually low risk, saliva can transfer bacteria, parasites, or viruses under some circumstances. Puppies, immunocompromised dogs, recently ill animals, or dogs with open mouth wounds are higher-risk contacts where minimizing direct mouth contact is sensible. Similarly, if a dog has had exposure to wildlife, rodents, or unknown substances, licking should be treated cautiously.

How owners should respond: practical, immediate actions

1. Observe and note context: Before intervening, look at who licks whom, body language before and after, and whether food, toys, or separation were involved. I typically watch the entire sequence for several seconds to tell affiliative from anxious or escalating behavior.
2. Interrupt calmly if escalation appears: If the recipient stiffens, snarls, or the interaction becomes prolonged and one-sided, calmly call the dogs away or use a neutral cue such as “let’s go” while offering a treat to redirect attention. Avoid shouting or sudden movements that could spike arousal.
3. Perform a basic mouth and face check: If you suspect injury, gently look for cuts, swelling, loose teeth, or foreign objects. If the dog resists a close exam or shows pain, don’t force it; note the signs for the veterinarian.
4. Document and monitor: Write down when and where it happened, who was involved, and the exact behaviors observed. Recurrent incidents with the same pattern are important to share with a professional.
5. Seek professional help if persistent or harmful: If licking becomes compulsive, leads to injury, or emerges alongside aggression or marked behavior change, consult your veterinarian to rule out medical causes and then a certified behaviorist if needed.

Training strategies and environment tweaks to reduce unwanted licking

Prevention and gentle shaping are often more effective than punishment. Supervised, gradual introductions help dogs build a positive history so mouth-licking appears within a calm, predictable context instead of a tense, competition-driven one. I start many introductions on leash at a distance where both dogs are relaxed, rewarding calm attention and moving closer only when both show neutral or friendly signals.

Teach and reinforce alternative cues that interrupt or replace mouth-licking when it’s inappropriate. “Leave it,” “sit,” and a reliable recall can redirect a licker to a more appropriate behavior and give the recipient space. Use high-value treats and clear, consistent reinforcement so the cue becomes more rewarding than the licking ritual.

Manage resources to avoid situations that tend to trigger mouth-focused behaviors. Feed dogs separately when introducing new diets or high-value chews, and remove toys or bones that create competition. Provide enrichment — food puzzles, varied walk routines, and safe chew items — to reduce boredom-driven licking that can escalate into a compulsive pattern.

If stress seems to drive the licking, address the stressors: shorten or change exposure to triggers, use desensitization and counterconditioning under a professional’s guidance, and create quiet zones where a dog can retreat without being followed or pestered by other dogs.

Recommended gear and safety tools for safer interactions

Several practical items make managing mouth-licking safer and simpler. A soft basket or training muzzle can be useful for short-term safety if you need to examine mouths or separate dogs after a fight; use muzzles only after desensitizing the dog so the tool itself does not increase stress. Barriers and baby gates let dogs see each other without direct access, useful during gradual introductions and when one dog is recovering from a medical issue.

High-value treats and durable toys serve as redirection tools and positive reinforcement for alternative behaviors. When you ask a dog to “leave it” or to come away, having a predictable, valuable reward speeds learning and reduces the temptation to inspect another dog’s mouth. Finally, basic first-aid supplies — gloves, antiseptic wipes, saline, and wound dressings — are worth having on hand to manage superficial mouth injuries until you can get veterinary care.

If it keeps happening — troubleshooting and when to get professional help

If mouth-licking remains frequent, one-sided, or leads to injury, the path forward is assessment and a coordinated plan. Start with a veterinary exam to rule out pain, dental disease, or systemic illness that could make a dog more reactive to mouth contact. If no medical cause is found, a behaviorist who works closely with veterinarians can assess the triggers in the home environment, design behavior modification steps, and suggest training protocols tailored to the dogs’ learning styles and daily routines.

Behavioural change often combines management, training, and environmental enrichment. In many cases, simple changes — staggered feeding, supervised and structured social periods, reliable alternative cues — reduce problematic licking substantially. In more entrenched cases, a graded desensitization plan, possibly paired with short-term anxiety medication under veterinary supervision, can help a dog learn different responses.

Sources, studies, and expert guidance

• Merck Veterinary Manual: “Normal and Abnormal Behavior in Dogs” — Merck Veterinary Manual, Merck & Co.
• American Veterinary Medical Association (AVMA): “Zoonotic Diseases and How They Spread” and client resources on normal dog behavior — AVMA.org
• American College of Veterinary Behaviorists (ACVB): Public resources and how to find a board-certified veterinary behaviorist — dacvb.org
• Bradshaw, J.W.S. & Nott, H.M.R., chapter on social behavior in The Domestic Dog: Its Evolution, Behaviour and Interactions with People (1995), edited by J. Serpell
• Overall, K.L., Clinical Behavioral Medicine for Small Animals, 2nd edition — a practical veterinary behavior textbook