Let’s talk about dog butt sniffing. Your dog putting their nose to another dog’s near end may seem gross, or cause awkward moments at the dog park. But for dogs it is quite natural—even important.

“When we, as people, meet someone new our first impression is based on sight,” says Dr. Shannon Barrett, Charleston-based house-call veterinarian and owner of Downward Paws. “Dogs are different, their first impression is formed by smelling each other.”

And it’s specifically scents in the anal sac that can tell one dog a lot about another, from age to aspects of personality to diet. In other words, your dog can learn a lot of helpful information through a good sniff.

With the help of Dr. Barrett, we’ll take a deeper look at why dogs sniff derrieres, and what information they glean from this behavior. Plus, we’ll examine how to discourage enthusiastic butt sniffing when it’s just not appropriate.

6 Reasons To Explain Why Dogs Sniff Butts

There are biological and social reasons for why dogs greet each other with sniffs back there. “Dogs use their superior sense of smell to gain information about one another,” says Dr. Barrett. “When one dog sniffs another dog’s bottom, it’s similar to reading a biography about the other animal.”

Dogs’ sense of smell is extraordinarily powerful

Perhaps if we had such powerful noses, we’d also be sniffing around! “[Dog’s] sense of smell is estimated to be between 10,000 and 100,000 times more powerful than ours, and this is because dogs have more olfactory cells than we do. Olfactory cells allow us to detect smells, and the more olfactory cells you have, the better you can detect odors,” says Dr. Barrett. Dogs also tend to have longer noses than us, giving them more ability to sniff, and dog breeds with particularly long noses are exceptionally good sniff detectors.

“Dogs are also right-nose dominant, meaning they start smelling with their right nostril first. They will switch to the left nostril if the scent is pleasing or familiar, such as food. But if the smell is new or upsetting, they will continue to use the right nostril,” says Dr. Barrett, who explains that the right side of a dog’s brain processes new information, while the left side is for information that’s familiar.

Additional scent receptors trigger dogs’ brains

Dogs possess a Jacobson’s organ (which does not exist in humans) and provides a way to interpret smells—and also plays a key role in why your dog loves licking! Located in the roof of the mouth, pheromones enter through the mouth before traveling to the brain for interpretation. “This explains why dogs often open their mouths while sniffing another dog’s rear end as they are using Jacobson’s organ,” says Dr. Barrett.

“Once dogs detect pheromones using their Jacobson’s organ, signals are rapidly transmitted to their brain and cause an emotional reaction. This is why dogs suddenly react to other dogs’ pheromones without thinking.”

Dogs use bottom sniffing to identify other dogs

In most cases, sniffing another dog’s behind is perfectly normal and an important part of dog socialization. Where humans usually spot a friend, neighbor or casual acquaintance by facial recognition, dogs use their superior sense of smell. This helps them to detect scents that are a bit like canine version of calling cards, unique to each dog.

“Dogs have scent glands around their mouths, paws, and near their rear ends,” says Dr. Barrett.

“Every dog has its unique scent that can be used to identify them to other members of the pack or species,” says Dr. Barrett. Because of this, scent has a very important role in communication. And, while us pet parents would use words or body language, Dr. Barrett says that dogs rely on a sense of smell to make sense of who they’re engaging with.

Canine anal glands contain detail-revealing pheromones

There are two key parts of the body that play a role in how dogs discern information from the rear. First are the anal sacs, which are small glands on either side of the anus that allow communication through smell. Dr. Barrett says these glands secrete oily fluid with information-packed pheromones.

Here are some examples of information a dog receives from pheromones:

• Health status
• Diet
• Age
• Gender
• Reproductive status
• Mood or emotional state

These scents and pheromones combined tell dogs so much more than, Dr. Barratt tells us dogs can even learn about the areas other dogs frequent. As a dog parent, you’ve probably seen your dog using scent to mark their territory or sniff around some particular outdoor spots, gathering information about another dog who may have marked or gone potty.

“So next time your dog is interested in another canine companion’s rear end, don’t worry; they’re just exchanging information,” says Dr. Barrett. “Or in our terms, asking their canine friend, ‘tell me a little about yourself.’”

The way a dog sniffs butts demonstrates their place in the social structure

Another way dogs may use scent is to establish dominance. “When two dogs meet, they will take turns sniffing each other’s bottoms to learn more about who they are and where they come from,” says Dr. Barrett. “This behavior is thought to be linked to dominance; the dog that sniffs first is generally considered dominant over the dog that gets sniffed first.”

Upon meeting another dog, you may notice your pup displaying additional body language indicating whether or not they want to be sniffed, a.k.a. introduced. Dr. Barrett says dogs that block access to their bottoms by putting their tails down, turning away or backing up, are indications of feeling threatened or uncomfortable. Additionally, your dog may look away from an approaching animal or appear to stiffen their posture, as if preparing for a fight, she says.

On the other side of the coin, inviting body language indicates a desire to engage. For example, Dr. Barrett says direct eye contact, tail wagging, or a tail held high indicate confidence for an approach.

“When your pup sniffs another dog’s bottom, they engage in an ancient canine tradition of exchanging vital information about themselves that helps them build relationships and navigate the world around them,” says Dr. Barrett—and that includes doggy social etiquette.

A dog sniffs butts when it’s looking for a mate

Another reason dogs sniff from behind is to determine if their dog companion is taken. “Dogs also use their sense of smell to tell if another dog has been in their area and to determine if a potential mate is available or taken,” says Dr. Barrett. She explains that, for example, in female dogs, her scent can let other dogs know if she’s been around a male dog and is unavailable.

However, sometimes this behavior of sniffing backsides can cross over into unwanted sexual behavior. The Jacobson’s organ plays an important role here. In some cases, how the organ functions can lead to increased sexual behavior, in other cases, malformation may mean a total lack of sexual behavior.

According to Dr. Barrett, here are some signs that your dog is crossing the line:

• Excessive or repetitive sniffing
• Frequent attempts to mount the other dog
• Aggressive posturing toward other animals/people while engaged in bottom sniffing
• Growling or baring teeth during the interaction
• Overall tense body language due to anxiousness or aggression

“If your pup exhibits these behaviors during interaction with other animals, you must step in before things escalate further,” says Dr. Barrett. “The owner should stop reinforcing the behavior immediately and redirect their pup’s attention elsewhere.” Try redirecting your dog right away with a trick, toy, or treat.

Is Mutual Butt Sniffing Acceptable Behavior?

It’s important to remember that dogs sniffing each other’s bottoms is normal. It is neither good nor bad, but simply how dogs engage with each other and learn information. As it is an instinctual and standard behavior for dogs, training them out of it is not necessary. However, there are times when this behavior is not acceptable and needs to be addressed.

“When two dogs engage in mutual bottom sniffing, it is important to watch closely for signs that one or both dogs may be uncomfortable,” says Dr. Barrett. This can include signs of fear, threat, or aggression, such as cowering, avoiding eye contact, tail tucking, lying down on the side, growling, snapping, or raised hackles on the back. “In these instances, you should use a firm voice to stop the activity and separate the two animals if necessary,” she says.

It’s important for pet parents to also be conscious of their own body language in dog interactions. Tension and anxiety on our part can lead our dogs to take cues from us and become uncomfortable. “We call it ‘feeding it down the leash,’” says Dr. Barrett. “If you get anxious, your dog will feel anxious and think, ‘My owner is worried, so there must be something to be on guard about.’”

Be sure to also pay attention to over exuberance when dogs meet and greet. Excessive jumping and barking can also lead to aggression and Dr. Barrett advises interrupting this behavior as well with redirection.

Why Your Dog Is Sniffing Your Butt And Crotch

If the primary glands of information for dogs are in the anal sacs, then for us humans, our glands that tell the most about us are in the crotch. Which is why we’ve all had to redirect dogs away from that area at some point. “Dogs have a much stronger sense of smell than we do and can detect far more information from these glands than we ever could,” says Dr. Barrett.

She points out that dogs can tell if a person is happy or sad based on the scents of pheromones or hormones. Additionally, they can also sense some pretty private aspects of our lives: “A dog’s nose is so sensitive that they can detect changes in a woman’s body chemistry even before she knows she’s pregnant,” says Dr. Barrett. “As for menstruation, dogs can detect changes in a woman’s hormone levels due to her menstrual cycle, leading them to show more affection towards her during certain times of the month.”

The following are some of the reasons why our dogs love to give us a sniff in rather private places.

Your dog is sniffing you because they recognize and love you

“Dogs are social animals, and they like to stay connected with one another by exchanging smells,” says Dr. Barrett. “So when your dog gives you a good sniffing, they can express their love and appreciation for having you in their lives.”

Your dog is trying to work out a range of things about where you’ve been and what you’ve eaten

“Dogs have over 300 million scent receptors in their noses, significantly more than humans have (we only have six million). That’s why they can pick up on smells we don’t notice,” says Dr. Barrett. “In particular, they can tell if a human has recently eaten something by picking up traces of food or drink in the air. They can also tell if someone has recently come into contact with another animal or person by picking up on smells that are unique to those individuals.”

Your dog is trying to work out if everything is okay

“Dogs have an incredibly keen sense of smell, so much so that their noses can pick up on subtle changes in our scent that indicate stress or illness. This means that your dog may use their nose to monitor your well-being. They may also be able to determine whether or not something in our environment is making us stressed or anxious,” says Dr. Barrett.

Your dog is trying to shape up the safety of a new or returning visitor

“By sniffing someone’s bottom, [dogs] can pick up on subtle changes in a scent that can tell them about gender, age, and even health status. By analyzing this information, they can decide if the person is friendly or dangerous,” says Dr. Barrett. “Additionally, since dogs can detect pheromones and other chemicals in the environment, they may even be able to tell if someone has been in contact with another animal or person recently.”

Your dog is trying to calm themselves after being away from you

“When we greet our pets after being away from them for even a few hours, it’s not uncommon for them to move straight towards our backside for more detailed analysis. This behavior is usually accompanied by tail-wagging or other signs of joy,” says Dr. Barrett. “There’s no need to feel embarrassed if a curious dog gives your bottom an extra-long sniff during your reunion. It might be their way of saying, ‘I missed you!’”

How to Stop Dog Butt Sniffing

Though our dogs sniffing us back there may be a sign of affection, that’s not necessarily what our visitors want! What’s polite in dog language doesn’t always translate for us humans. In which case, it’s important to train our pups to avoid this behavior when meeting other people.

Positive reinforcement is a great tool for helping our doggos avoid this sniffing behavior when guests arrive. “If your pet is trained to sit when guests enter your home, reward them with a small treat every time they do so successfully,” says Dr. Barrett. “This will reinforce the correct behavior in your pet’s mind and make it more likely that she will remember it the next time a guest enters your home.” She also advises quickly distracting dogs with toys or treats if they start to sniff, in order to interrupt the behavior. “It’s essential to remember that this type of training takes patience and consistency from both you and your pet,” says Dr. Barrett.

When in doubt, plenty of exercise throughout the day always helps dogs achieve some calm in otherwise exciting situations. As Dr. Barrett points out: “The more tired they are at the end of the day, the less likely they are to jump all over guests when they come over.”