Why Does Dog Hair Stand Up? (Spine, Tail, Playing)

We’ve all seen it happen many times before but still might wonder why a dog’s hair stands up. It can stand up on their spine, back, near the tail, when they’re playing, barking, and when they get mad or even when sick. It can happen a lot in different situations.

But why does it stand up like this?

Dogs’ hair stands up for reasons including a sign of fear, anxiety, excitement, sexual arousal, aggression, or dominance. In simple terms, your dog’s hair stands up in response to your dog’s emotional state, so it can act as a warning to you, and other dogs.

Knowing why your dog’s hair is standing will help you understand and communicate better with your pet. Below I’ve outlined facts about this “spiked hair” phenomenon in dogs and when you should be worried.

Why you dog’s hair is standing up on the spine or near the tail

There are certain things we observe from our dogs that are truly baffling. One of them includes how the hair on their back can stand up along the spine or down near the tail, whilst the rest of the fur remains flat. There’s a name for these specific hairs: hackles.

Raised hackles are mostly concentrated on the neck area, shoulders, and top of the body. That’s why you often notice a dog’s hair standing up near the tail or on the back.

Contrary to what many people think, erect hackles don’t automatically mean a dog is in an aggressive mood. It’s not always an aggression thing when you see the hair on your dog stand up.

Our canine friends experience several emotions that manifest in different ways, e.g. like through raised hackles and hair standing up. But it’s not your dog consciously lifting the hairs.

The whole “hair-standing-up” mystery happens naturally. Same way you get goosebumps. Your dog can’t stop the fur from standing.

The scientific term for this natural process is piloerection.

“Pilo” is the medical word for hair, and erection means upright. So, the scientific name makes perfect sense.

Piloerection is triggered by the emotional situation your dog is in. It’s a complicated process involving your dog’s nervous system getting activated, adrenaline flooding their body, brain signals, and a lot of other complex stuff.

But here’s the simple part. These physiological activities make the tiny muscles that sit on your dog’s hackles contract. And because of these contractions, the hairs stand up on their back.

Since all dogs experience various emotions, it’s correct to say that all breeds can get raised hackles. The only difference is that it’s more obvious in some breeds compared to others.

It can be hard to spot these raised hairs on dogs with long and overly fluffy hair. But for breeds with short hair, you’ll quickly notice what’s happening.

Raised hairs for sure mean your dog is experiencing a particular emotion. But to know what exactly this emotion is, you need to consider the context and pay attention to your dog’s body language.

And if whatever emotion your dog is feeling is too overpowering, the hairs can stand up on all the hackles’ “hotspots” (neck, shoulders, back, tail). Not just in one place.

Why dog’s hair is standing up near the tail

That said, here are some of the common reasons why a dog’s hair stands up:

1. Hair stands up when scared

Many things can put your furry pal in a state of fear. It can be the loud sound of fireworks, balloons, being at the vet’s office, or simply watching the bully dog next door barking through the window.

Such fearful experiences can trigger a dog’s hair standing up. You will also notice your furry friend showing other signs of fear, for instance:

  • Whale eyes (The whites of the eyes showing more than usual).
  • Tail tucked between their legs.
  • Ears pinned back.
  • Pacing around.

2. Hair stands up when playing and excited

Raised hackles are common in dogs that are super excited. You may spot the erect hairs if your dog is having a blast playing with you or another friendly dog.

Your furry friend may be extremely happy to meet a new dog friend at the park. This happy moment can translate to hairs going up.

Besides the raised hackles, you’ll observe your furry pal displaying positive body language like being jumpy, lots of high-in-the-air tail wagging, tongue sticking out, and all that good stuff!

So, if you dog’s hair is standing up when playing, it’s a good sign and nothing to worry about.

3. Hair stands up when aggressive

When your dog feels aggressive (perhaps they’ve spotted a stranger they don’t like or another dog has angered them), the hairs can stand up when they are mad.

And since your dog will want to warn the other party to “keep off”, the intense anger will make the erect hairs appear puffier. This will give your dog an intimidating look as is designed to make them look larger in front of the other dog.

Your canine friend will also display typical aggression signs — like a stiff body posture, growls, and a hard stare.

barking dog
Dogs’ hair can stand up when they get mad and bark (https://pixabay.com/photos/labradoodle-dog-labrador-muzzle-1499231/)

4. Hair stands up when insecure

Your lovely furry friend may be the most confident canine of them all. But if a certain situation makes them feel insecure, the erect hairs can appear.

For example, if your small dog bumps into a much bigger dog during a stroll, they might feel somewhat inferior. As their body processes this uncomfortable emotion, the hairs can go up.

5. Hair stands up when anxious

Dogs also experience raised hairs when anxious. For instance, if your dog isn’t properly socialized and you take them to the park, the presence of many people and other dogs can trigger the erect hackles and make their hair stand up along the back spine and near the tail.

And when their hair stands up due to anxiety, their body language will also tell it all: whining, looking away, lip licking, and a lowered posture, among other signs.

6. Hair stands up when shocked and surprised

Our furry friends don’t like being caught off guard.

When something unexpected happens, for instance, walking up to them and blowing air on their face. The sudden shock can make the hackles point up.

Since almost all dogs tend to react negatively to surprising situations, the raised hackles may be accompanied by behaviors like nipping or barking, or growling.

7. Hair stands up when asserting dominance

Your four-legged friend may want to act dominant in particular situations.

For example, when they’ve just met a new dog and want to be the dominant one in the newly found friendship. In this case, your dog will be the first to perform the classic butt sniff greeting so that the other dog becomes the submissive one from the word go.

And while doing the sniffing, their hair can stand up.

You may also observe the erect hairs when your furry friend is trying to act dominant with you, for example, when ignoring your commands.

8. Hair stands up when eager to mate

If you have an unspayed or unneutered four-legged buddy, they often experience strong sexual urges when the estrus season arrives.

Your unspayed furry queen will be thrilled to meet a male dog who will sort out her sexual needs. And if your furry pal is an unneutered male, sniffing out a female dog in heat can make them ecstatic.

This overwhelming sexual excitement often makes their bodies experience a flood of adrenaline, triggering the hairs to point up.


Why do dogs’ hair stand up when barking and mad?

This depends on what emotion your dog is experiencing that’s causing the barking. Our furry friends bark for many reasons — like fear, aggression, excitement, anxiety, or surprise.

By paying attention to the context of the barking and your dog’s body language, you will know what emotion is making your dog’s hair stand up.

Why do dogs’ hair stand up when playing?

The reason is that they’re excited. As discussed earlier, our canine friends normally get raised hackles when in a happy mood.  If they are enjoying a great game, their hair may stand up due to excitement.


The hairs along your dog’s back stand up because your dog is either excited, anxious, angry, sexually aroused, wants to act dominant, or feels insecure.

The only accurate way to know what emotion is truly causing the raised hairs is to observe your furry friend’s body language and pay attention to what’s happening around them.

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Image in header via https://pixabay.com/photos/dog-canine-growling-bark-barking-86422/

Marc Aaron

I write about the things we've learned about owning dogs, the adventures we have, and any advice and tips we've picked up along the way.

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