Fear Periods in Dogs: Why Did My Puppy Turn Into a Scaredy Cat?

Dog Behavior


Erin Jones

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fear periods in dogs

Wondering why your spunky pup has suddenly transformed into a skittish scaredy-cat? It’s not a personality change — it’s science!

You see, all puppies go through a sensitive period of socialization. This starts at 3-weeks of age and lasts until 16-weeks of age. 

This socialization window is a critical period during which it’s essential that you socialize your puppy by introducing her to positive interactions with her environment. This will help ensure your pooch enjoys proper emotional and mental development.  

You’ve likely heard at least a little bit about the importance of socializing puppies at a young age during this socialization window.

But puppies also go through additional canine development stages, called fear periods. 

These are times in your puppy’s life when she will be particularly sensitive to bad experiences. And these bad experiences could influence her into adulthood.

Below, we’ll explain everything you need to know about fear periods, so that you will know how to care for your puppy during these critical times.  

Fear Periods in Dogs: Key Takeaways

  • Puppies experience two fear periods while growing up, during which they’re particularly likely to be frightened by various things.
  • Things that frighten your pooch during these time periods may continue to scare her for the rest of her life.
  • It is important to introduce your puppy to new and novel things in a positive manner during her fear periods.

What Are Fear Periods in Dogs? 

From time to time, you may notice that your once confident and curious pup suddenly seems shy, nervous, and unsure. 

You may find yourself asking, “why is my puppy scared of everything?” 

Don’t worry: She is likely experiencing a fear period. And it’s perfectly normal!

Fear periods are times during which puppies become more sensitive to a variety of external stimuli

Puppies experience two fear periods during their development, and each fear period lasts for about 2 to 3 weeks, on average. 

We’ll talk about when these fear periods occur later on, but for now, let’s talk about what fear periods look like in your pup.

What Does a Fear Period Look Like?

The signs of a fear period can be obvious in some dogs, but more subtle in others.

During a fear period, your pup may react by cowering, shying away, hiding, or trembling at things that didn’t bother her previously.  

Fear periods can also manifest as defensive behaviors such as barking, growling or lunging. Sometimes, dogs who are fearful bark, growl or even lunge at whatever, or whomever, has spooked them.

dog suddenly afraid

This could sometimes be misinterpreted as confidence, or “cheekiness” when in fact it’s an emotional and reflexive reaction of fear.

Some four-footers may not exhibit these outward or more obvious signs of fear during their fear period, so you may miss them altogether.

This is particularly true for owners who don’t notice the more subtle signs of stress, such as:

  • Lip licking
  • Yawning
  • Looking away
  • Freezing or moving more slowly
  • Holding her ears back
  • Tucking her tail
  • Panting
  • Showing the whites of her eyes
  • Refusing treats
  • Lowered body postures
body language fear signs

Every pup is an individual. You’re the best judge of what is normal for your pooch and what isn’t.

Why Fear Periods are Dangerous for Your Dog’s Development

During a fear period, your pup is more vulnerable to feeling traumatized by bad experiences.

This may include things like being approached by a stranger, interacting with another dog who is not so polite (just one reason why you should probably keep your pup away from the dog park), hearing loud noises like fireworks, or experiencing other scary situations.

Some of the more common things for dogs to be fearful of are:

  • Strangers
  • Being handled/touched
  • Loud noises
  • Unfamiliar objects
  • People coming to the door
  • Traffic – trucks, busses, trailers, for example.
  • Children
  • Men

Dogs (as well as most other animals) can learn quickly to make a negative association with something that is overly scary or painful. 

This feeling might stick with your pup into adulthood. And it only takes one bad experience during this impressionable time to have lifelong effects.

For wild dogs, these fear periods are what keep young dogs on alert and teach them valuable lessons about what areas and objects to avoid.

Owners need to work hard to navigate these built-in fear periods, so they can prevent their pup from becoming traumatized by bad experiences.

dog fear periods

For example, perhaps nail trims were no big deal for your doggo in the past and you’ve been working on getting her comfortable with the whole procedure since bringing her home at 8-weeks of age.

But, during a fear period when she was feeling extra stressed about having her paws handled, you accidentally clipped one of her nails a bit too close. 

This could cause her to make a negative association with the nail clippers, her paws being handled, or even with you. This is similar to perhaps what a child would experience when touching a hot burner on the stove for the first (and probably only) time. 

The evolutionary factor here is that young animals (including humans) create an emotional reaction to something that is dangerous or can hurt them. This “single event learning” can have a lasting impact on how your pup feels about nail trims forever.

This close nail trim may not have had quite the same impact at another point in time. Had your pooch not been in a fear period, she may have been able to “shake it off” much more easily with some cookies and extra pats.

When Do Fear Periods Occur in Dogs? 

Your puppy will experience two fear periods in her lifetime. We’ll explain when these happen and what to expect below. 

First Fear Period

The first fear period happens at 8 to 10 weeks of age.

This initial fear period often goes unnoticed because your puppy is still learning and exploring in a cautious and curious manner. She also doesn’t have a history of certain expected responses or behaviors since most experiences are still new to her. 

Because the first fear period occurs during this critical puppy socialization period, you will want to approach all of her new experiences with ample support, encouragement, and understanding.

And treats! Lots and lots of treats!

Second Fear Period

The second fear period is a little more unpredictable and may feel like it comes out of nowhere. In fact, it can occur anywhere between 6 and 14 months of age. That’s a lot of variability! 

However, it’s potentially easier to notice your puppy’s second fear period because you may witness a more drastic change in her behavior. Your once confident and ambitious pup may suddenly become reserved, reactive, and seemingly transformed into an aggressive puppy in what feels like the blink of an eye.

What Should You Do During Your Dog’s Fear Periods? 

Most of the time, you can wait it out as these fear periods pass. No harm done, and your pupper will regain her canine confidence and be ready to take on the world again. 

However, because there is a potential to make a lasting negative association with a single bad experience during this time, you want to approach this period of time with some understanding and extra preventative measures.

If you suspect your pup is experiencing a fear period, here are a few do’s and don’ts:


  • Allow her to explore the world at her own pace.
  • Comfort your puppy when she is feeling scared.
  • Pair scary situations, noises, people or objects with treats. This will help her to make positive associations.
  • Build her confidence through training using positive reinforcement.
  • Avoid traumatic experiences. Consider staying away from dog parks and busy streets where there is more potential for a bad experience to occur.
  • Studies (including this one and this one) show that the use supplements such as Zylkene or L-Theanine can reduce stress and promote relaxation and might be useful during this time.
  • Studies also suggest that the use of a D.A.P. (Adaptil), a synthetic appeasing pheromone, may reduce stress in dogs and again, may benefit your pup during her fear period. You might also consider incorporating CBD or calming supplements (with your vet’s OK) into your pup’s regiment around her fear periods.


  • Make a big deal when she reacts unfavorably.
  • Punish your puppy for barking, lunging or growling.
  • Push her into uncomfortable situations, such as forcing her to accept being handled, walked, or to interact with strangers.
  • Ignore her when she is seeking you out for comfort.
  • Get frustrated. It’s ok!
  • Over-expose her to frightening stimuli. In fact, try to avoid scary things altogether.


It is important to understand your dog’s different developmental stages of life so that you can be prepared to support her in the ways she needs. 

Did you experience a fear period with your dog? Did you know what was happening, or did it come as a total surprise? Did you both come out the other side unscathed? 

We would love to hear how you survived your pup’s fear periods!

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Written by

Erin Jones

Erin is a Certified Professional Dog Trainer and a Certified Dog Behavior Consultant. After completing her MSc in Anthrozoology, Erin moved to New Zealand early in 2019 to complete her PhD at the University of Canterbury - New Zealand Centre for Human-Animal Studies. Her research focuses on the ethics and social constructs of the human-dog relationship and humane training practices. She lives in Christchurch, New Zealand with her husband and their dog, Juno.

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