Skip to Content

Dogs Sniffing Aggression: 9 Reasons Why Dogs Get Triggered

Dog Sniffing Aggression

Dogs greet each other by sniffing one another…

However, some dogs are extra reactive to that interaction. 

They don’t want to participate in such…

And they display that refusal aggressively.

Now, why do they do that?

Continue reading to discover:

  • 9 reasons why dogs get triggered by sniffing.
  • Why do dogs sniff each other in the first place.
  • 3 kinds of aggression that can explain this behavior.
  • How you can unintentionally escalate your dog’s aggression.
  • And much, much more…

Why do dogs get aggressive when other dogs sniff them?

Dogs get aggressive when other dogs sniff them because they’re scared or reactive. It could also be due to redirected, social, or pain-elicited aggression. Such a reaction could be from poor socialization, being on a leash, or your involvement. Dogs in heat tend to react the same way, too.

9 reasons why some dogs get aggressive when other dogs sniff them

#1: Fear

Sometimes that aggression isn’t from anger.

It can be from another emotion…

What am I talking about?

Your pooch could be fearful of the canine that’s sniffing them…

“But, it’s just a sniff…”

Regardless, your pup is still scared.

And yes, even a sniff can set off fear in dogs.

How so?

Let’s take it from the Merck Vet Manual‘s definition of fear:

This emotion can manifest as a response to a threat. That trouble can either be actual or perceived.

The latter is why even a sniff can set off fear in dogs. It can manifest even more quickly if the dog’s unfamiliar to them.

That’s because not knowing can trigger a dog’s aggression.

According to research, strangeness brings competition between two unfamiliar dogs. 

That’s also why most dogs are aloof in new environments.

Moreover, your pup doesn’t know the other dog’s intention that’s sniffing them.

Now, your pooch thinks there’ll be a threat that’s coming towards them.

With that, they’ll react aggressively to the sniff.

They’re also more prone to be aggressive if the sniffing dog has cornered them.

This is called the ‘fight response.’ It’s one end of the so-called fight or flight response.

Your pooch that feels cornered can’t pick the second choice. So, they result in fighting instead…

And that fighting requires them to be aggressive.

“Now, what does sniffing mean in dogs in the first place?

Why do they do it?”

Sniffing is a dog’s way of knowing another

Think about how you meet other people…

You say ‘hello‘ or shake their hands. Then, you evaluate them by the way they talk or dress…

Well, dogs have their own way of doing that, too.

Our four-legged friends assess each other differently.

It’s so peculiar…

They do it by sniffing each other.

According to VCA Hospitals, a dog’s olfactory ability enhances their communication.

How so?

It involves biochemical compounds that result in chemical communication.

With that, a simple whiff can help Fido identify the other canine’s:

  • Mood.
  • Health.
  • Gender.
  • Food preference.

Furthermore, there’s a question that dog parents always ask…

“Why do dogs specifically sniff each other’s bum?”

That’s because that’s where most of the identifying smells are…

It’s an anatomical explanation.

In your dog’s rear end lies the rectum. And inside of that are small sacs called anal glands.

These glands secrete a smelling substance.

The odor of each dog is unique.

That’s how canines determine if they’ve met the other before.

You might also ask: Why is my dog acting paranoid all of a sudden?

#2: Redirected aggression

Some Dogs Get Aggressive When Other Dogs Sniff Them Because Of Redirected Aggression

In some cases, the canine sniffing your pooch was just at the wrong place and time…

What do I mean?

I’m talking about how your pooch isn’t being aggressive to the sniffer in the first place. That their aggression is actually directed to something else.

Imagine this:

Say you’re outside, and Fido sees a cat on someone’s porch.

With that, your pooch gets aroused by the sight of the feline.

The cat is just there while your pup is on a leash.

Fido wants to pursue catto so badly…

They start to misbehave a little bit. They’re growling in a low voice, and their tail is wagging slowly.

Then, here comes the sniffer who picked the wrong time…

They sniff your pupper’s rear end, and your fur baby is taken aback.

That’s how the dog fight started.

Now, the point of imagining that scenario is to see things clearly. 

Your fur baby didn’t have a problem with being sniffed at all.

However, they’re indeed feeling aggressive. Only towards something else…

And when your pooch is approached, they got startled.

So, they reacted poorly to the interaction.

And, oh…

Poor canine friend whose intentions are pure…

Your pooch redirected their aggression towards the sniffer, resulting in something stressful…

#3: They simply don’t want to

Dogs are beings with limits, too.

However, they can’t directly say it. So, this fact is often overlooked.

Despite that, dogs actually try to tell us.

They use what they can, and that’s their body language.

In this scenario, your pooch decided to make use of social aggression

What am I talking about?

Well, it’s simple…

Your dog is clearly not up for the interaction.

They’re not in the mood to socialize or to be analyzed.

And now, the dog who continues to sniff them oversteps their bounds…

With that, your pooch has reacted aggressively to push the sniffing canine away.

Warning: You can also receive this type of aggression.

Yes, your dog loves you…

But like I said, they have their limits, too.

That’s why if you’re not mindful, you can be a recipient of this hostility.

Note: Your pooch isn’t challenging your dominance when this happens. They’re just a creature who’ll appreciate your respect for their boundaries.

So, you must avoid these types of interactions with your dog. If you do, you’ll prevent them from being hostile towards you:

  • Hugging them.
  • Scolding them.
  • Trimming their nails.
  • Taking their food away.
  • Threatening to hit them.
  • Getting a chew toy from their mouth.
  • Randomly touching their ears or feet.
  • Disturbing them while they’re sleeping.
  • Trying to carry them to a different place.

#4: Lack of socialization

Unfortunately, your pup is an awkward one…

They don’t know how to socialize properly.

With that, they react poorly to a simple greeting of a sniffing dog.

That’s among the many negative effects of poor socialization in canines.

Research tells us that socialization must start in puppyhood.

And that when a puppy is properly socialized, they’re less likely to show behavioral problems. Those include issues of aggression and fearfulness.

So, your poorly socialized pooch becomes awkward. They don’t know how to act around new canines…

Your pupper doesn’t know how to communicate with their fellow canines appropriately. That’s why they mistake sniffing for a threat.

Moreover, PetMD tells us the other consequences of poor socialization in dogs:

  • Getting easily scared.
  • Being afraid of strangers.
  • Being frightened of adventures.
  • Intense sensitivity towards sounds.
  • Having difficulty with being groomed.

#5: They’re in pain

Aggressive Dog Is In Pain

You know your fur baby is calm and gentle…

As their dog parent, you’re sure that your pooch is friendly with other dogs.

That’s why it shocked you when Fido reacted aggressively when a dog sniffed them.

If it indeed came to you as a surprise, then you should answer these questions:

Have there been any recent changes in your dog’s temperament? 

Are they more reactive than usual?

Is this sniffing incident an isolated case?

If the answer to the first 2 is a ‘yes,’ then a ‘no’ on the second…


Something has been causing your pooch to be more irritated.

“What could it be?”

Sadly, your pupper might be in pain.

It’s called pain-elicited aggression

As you claim, your pooch is usually gentle and friendly…

However, the pain has driven them to become suddenly aggressive.

This occurrence is called pain-elicited aggression.

Warning: You can receive this treatment from your dog, too.

Despite your relationship with them, they’ll still act aggressively towards you.

But don’t take it personally. That’s not Fido’s intention at all…

It’s their pain that drives them to act that way.

This study states that pain makes your dog feel more at risk. 

With that, they’re prone to express higher levels of anxiety. That also results in becoming more aggressive.

“But what exactly could they be feeling?”

According to experts, injuries and orthopedic issues are the most common reasons. 

Want to find out if this is the case?

Then, you must be more observant of your dog. 

Check to see if they’re showing any other signs of illness. Namely:

Reading tip: Why Is My Dog Suddenly Aggressive To Our Other Dog?

#6: She’s in heat

A dog in heat isn’t her usual self…

She’s going through drastic hormone changes in this process.

Such an experience causes her to become moody. She’s also more prone to be more irritable and nervous.

Moreover, she might even be in pain.

With that, she’s more likely to show aggression when she’s in heat.

Now, say you took your pooch in heat out for a walk.

Outside, her pheromones magnetize the male dogs.

They’ll go to her and sniff her.

However, your fur baby doesn’t enjoy this attention.

So, she becomes aggressive towards the male pooch.

If that happens, she’s in the early stage of her heat cycle.

It’s when they don’t allow mating yet. That’s why she’s hostile toward the male canine.

To understand even better, here’s…

The female dog heat cycle

According to the MSDVM, a female dog’s heat season is called the estrous cycle.

It has 4 phases. Namely:

Phase in the estrous cycleWhat happens
Proestrus(7 to 10 days)This is the start of the heat cycle. It’s the phase where she doesn’t allow mating yet. Her vulva is swelling and secreting discharge.
Estrus(5 to 10 days)The mating period. Secretion of bloody discharge lessens, then stops. This is the ovulation period.
Diestrus(10 to 140 days)The after heat period. The dog is either pregnant or resting.
AnestrusThe resting period. It occurs between the last diestrus and the next proestrus.

Read also: 17 Tips On What To Do When Your Dog Is In Heat (& Bleeding)

#7: It’s just an overreaction

Sometimes, your dog isn’t really being aggressive.

You just confuse it with their reactivity.

What is reactivity in dogs?

It’s when your pooch tends to overreact to normal things around them.

These reactions are:

  • Barking.
  • Lunging.
  • Growling.

So, when another dog sniffs your pooch, and they react that way…


Give your pup the benefit of the doubt for a while.

They’re not really being aggressive.

They just reacted poorly.

And if your dog is a reactive one, it’ll be tougher for you to do activities with them.

That’s because they might provoke other dogs with their response.

It can escalate to aggression, which can then create a fight between the dogs.

“What could’ve caused my dog to behave this way?”

PetMD tells us that reactivity can stem from poor socialization.

According to vets, poorly socialized dogs don’t have appropriate coping skills. That’s why they don’t know how to react to normal interactions properly.

#8: Leash reactivity


Another leisurely walk has turned into a stressful situation.

And it makes you think where you went wrong.

Fido is well-fed, healthy, and you put him on a leash…

Oh, wait…

The latter might be the reason for it…

You see, there’s something called leash aggression or leash reactivity in dogs.

It’s a commonly reported behavior by dog parents. And not only is it embarrassing, but it’s also dangerous.

PetMD says it’s because leash reactivity causes the following behaviors in dogs:

  • Barking.
  • Lunging.
  • Snarling.
  • Jumping.
  • Growling.
  • Pulling the leash.
  • Overexcited behavior.

Moreover, it can cause dog fights among the sweetest canines.

So, imagine this:

Your pooch is on a leash for their routine walk…

And it’s going great…

Until another canine shows up and they’re not constrained with a leash.

This canine decides to approach your pooch and sniff them.

Your fur baby hated the interaction. It’s obvious as they reacted aggressively.

“What’s with the leash that makes them react this way?”

The leash makes your pooch feel frustrated.

In the scenario I’ve given, the leash restricts their movements. Then, the dog sniffing them is free to roam around.

That creates annoyance on your fur baby’s end.

Moreover, the meeting also causes tension between the canines.

Now, brew those feelings together in your canine…

And boom…

There goes the so-called leash aggression.

#9: You played a role

You might be playing a role in this unfortunate interaction…

“Really? How so?”

I discussed leash reactivity in the previous section…

Frequently, such an interaction doesn’t normally escalate. 

Some dogs will show that they’re ready to attack but calm down after a few seconds.

Other times, the meeting will intensify due to your involvement.

Let’s play another scenario:

Your dog on a leash starts to bark at another canine that they see.

Then, that canine decides to get close to your pooch.

As the unfamiliar canine approaches, you notice your dog starts to be uncomfortable.

When the canine finally sniffs your dog, Fido starts snarling a little bit.

And so, you decided to take matters into your own hands.

You did so by pulling your dog’s leash. The reason for doing so is to have your pooch closer to you.

But it didn’t help. Instead, your pooch begins to fight the leash and jumps at the other dog.

Wanna know where you went wrong?

It’s when you tugged their leash.

According to vets, such involvement adds to the tension.

It also acts as a signal that your dog needs to be concerned.

Showing frustration or anxiety towards the interaction can escalate things, too.

Even your corrections or scolding during socialization can bring the same result.

So, be mindful of how you react so that your pooch won’t sense any urgency from you.