Why Dog Behavior Change After Vaccination And What To Do?

Are you concerned about how your dog will react after getting vaccinated? Vaccines are an important part of keeping your pup healthy, but they can also cause a change in behavior. In this blog post, we’ll discuss how your dog may act differently after receiving a vaccine, the possible causes of these changes, and how to help your pup adjust.

Vaccines can cause a range of reactions, from mild to severe. Some dogs might become more anxious or nervous, while others may become lethargic or disinterested in activities. Some may even show signs of aggression, such as growling or barking.

These changes in behavior may be due to the stress of the procedure, the ingredients in the vaccine, or the reaction to the vaccine itself. It is important to be aware of these behaviors and how to help your pup adjust. If you notice any changes in your pup’s behavior, contact your veterinarian to discuss possible treatment options.

In most cases, the behavior should resolve on its own after a few days. In the meantime, try to provide your pup with extra love and attention to help them relax. If the behavior persists, your vet may suggest medications or other forms of treatment. Ultimately, it is important to remember that vaccines are necessary in order to keep your pup healthy and safe.

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Why You Should Get Your Dog Vaccinated

Vaccination plays a critical role in protecting your furry friend from various life-threatening diseases, such as canine parvovirus, distemper, and rabies. By introducing a weakened or inactivated form of the pathogen into your dog’s system, vaccines stimulate their immune system to produce antibodies, equipping them with the ability to fight off these dangerous diseases effectively.

Here are some compelling reasons to get your dog vaccinated:

Protect your pup from serious illnesses: Vaccines shield your dog from potentially life-threatening diseases like rabies, parvovirus, distemper, and hepatitis. These illnesses can cause immense suffering and even be fatal. Vaccination is like a superhero shield, keeping your dog safe and healthy.

Ensure a longer, happier life: By preventing these diseases, vaccination allows your dog to live a longer, healthier, and more joyful life. Imagine all the tail wags, belly rubs, and adventures you can share with your healthy companion for years to come!

Contribute to herd immunity: When a high percentage of dogs in a community are vaccinated, it creates a protective barrier against disease outbreaks. This “herd immunity” effect safeguards not only your dog but also vulnerable puppies, older dogs, and dogs with compromised immune systems. Think of it as a team effort where everyone’s vaccinations contribute to a healthier community for all.

Peace of mind for you: Knowing your dog is protected from preventable diseases brings immense peace of mind. You can relax and enjoy playtime, walks, and cuddles without worrying about your furry friend contracting a serious illness. It’s like a weight lifted off your shoulders, allowing you to focus on creating happy memories with your canine companion.

It’s the responsible thing to do: Vaccinating your dog is not just about protecting your pet; it’s also about being a responsible member of the pet community. By ensuring your dog is vaccinated, you’re helping to prevent the spread of diseases and keep the entire community healthy and happy. Think of it as your contribution to a wagging-tail world!

Temporary Behavior Changes: A Normal Response To Vaccination

It’s not uncommon for dogs to exhibit temporary behavior changes following vaccination. These changes can be attributed to the immune response triggered by the vaccine, which may cause your dog to feel a bit under the weather. Some dogs may experience mild discomfort, such as localized pain or swelling at the injection site, which could lead to temporary changes in their demeanor.

Common Behavior Changes and Their Underlying Causes

Some of the most common behavior changes observed in dogs after vaccination include:

  • Lethargy: Your dog may seem more tired than usual due to the energy their body is using to mount an immune response.
  • Decreased appetite: As your dog’s body focuses on fighting off potential pathogens, they might show less interest in food.
  • Mild fever: A low-grade fever is a normal reaction to vaccination, and it may cause your dog to be more irritable or less playful than usual.
  • Increased sensitivity: Your dog might be more sensitive to touch or handling, particularly around the injection site.

The Science Behind Your Dog’s Mood Swings After Receiving Vaccines

The Body’s Natural Response: Immune Activation

When a dog receives a vaccine, their immune system is stimulated to produce an immune response. This is an essential process that helps their body recognize and fight off the specific pathogens targeted by the vaccine. However, this immune activation can also cause temporary physiological changes that may result in mood swings or other behavior changes in your dog.

Inflammation and Hormones: The Role of Cytokines

During the immune response, the body produces cytokines – small proteins that act as messengers between cells. Cytokines play a crucial role in regulating inflammation and controlling the immune system’s actions. Some cytokines, such as interleukin-1 (IL-1) and interleukin-6 (IL-6), can affect the brain and cause temporary changes in behavior.

These cytokines can cross the blood-brain barrier and influence neurotransmitter systems, which in turn can impact your dog’s mood and behavior. For example, increased levels of IL-1 have been associated with fatigue and reduced activity, while IL-6 may contribute to feelings of malaise or irritability.

Stress and the Vaccination Experience

The experience of visiting the vet and receiving a vaccine can also be a source of stress for your dog. Stress can cause the release of cortisol, a hormone that prepares the body to respond to threats. Elevated cortisol levels can result in increased anxiety or fearfulness, making your dog more prone to mood swings after receiving their vaccines.

Individual Factors: Why Some Dogs Are More Affected Than Others

Each dog is unique, and their response to vaccination can vary depending on factors such as age, breed, overall health, and previous experiences with vaccinations. Younger dogs or those with a history of adverse reactions may be more susceptible to mood swings following vaccination.

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Why Has Your Dog’s Behavior Changed Since Vaccination?

Why Has Your Dog’s Behavior Changed Since Vaccination?
Why Has Your Dog’s Behavior Changed Since Vaccination?

Not Feeling Well

After a dog is vaccinated, he may experience some behavior changes. He may seem tired or sleepy and less active than usual. He may also seem irritable or uninterested in playing, or he may be clingy and want to be around his owner more. These behavior changes may be due to the stress of the vaccination, or to the body’s natural response to the vaccine.

In any case, it is important to keep an eye on your dog and make sure he is comfortable and not in pain. If he continues to seem unwell for more than a few days, it is best to contact your vet for a checkup.


Hypersensitivity reactions and behavioral changes can occur after a dog is vaccinated. Dogs may become more anxious, more sensitive to sounds, startle more easily, or may even become aggressive. These changes may last for a few hours or days after the vaccination, or may even last for weeks or months.

The changes are usually mild and will go away on their own, but if they become more severe or last for a long period of time, it is important to talk to a veterinarian. Vaccinations are an important part of a pet’s health, but it is important to watch for any changes in behavior after the vaccination is administered.

An Allergic Reaction

When a dog is vaccinated, their behavior may change as a result. Dogs may become more lethargic or even sick for a short period of time after receiving the vaccination. This is because the body is trying to adjust to the new substances in the vaccine.

In some cases, a dog may experience an allergic reaction to the vaccination, which can cause them to become more anxious or irritable. It is important that owners keep an eye on their dog for any signs of an allergic reaction and contact a veterinarian if any concerning changes in behavior are observed.


Inflammation and pain following vaccination can cause changes in a dog’s behavior. Dogs may become less active, more anxious, and more irritable due to the pain and discomfort caused by the injection.

They may also become clingier and more sensitive to touch or noise. If a dog is displaying signs of pain or discomfort after vaccination, it is important to speak with your vet about possible treatments to reduce the discomfort. Additionally, making sure your dog is getting enough sleep, exercise, and mental stimulation can help reduce the stress of vaccination and its side effects.

Is It Normal For A Dog’s Behavior To Change After Vaccination?

Yes, it is normal for a dog’s behavior to change after vaccination. After receiving a vaccine, dogs may experience some mild side effects such as lethargy, decreased appetite, and reduced activity levels. In addition, some dogs may become anxious, fearful, or display signs of aggression due to their discomfort.

This is usually temporary and will resolve itself within a few days. However, it is important to monitor your dog’s behavior after vaccination and contact your veterinarian if any changes seem concerning.

Will Your Dog’s Behavior Return Following Vaccination?

Explaining Dog Behavior Changes After Vaccination In Detail

Yes, it is possible that your dog’s behavior may return to normal following vaccination. After a dog has been vaccinated, it may experience some temporary side effects such as lethargy, mild fever, and slight discomfort.

These are all normal signs that the body is reacting to the introduction of the vaccine and will usually resolve within 1-2 days. If your dog does become lethargic or uncomfortable after vaccination, it is recommended that you speak with your veterinarian as they may prescribe a mild pain reliever to help your dog feel more comfortable. After the side effects of the vaccine have resolved, you should see your dog’s behavior return to normal.

How to Support Your Dog after Vaccination

After your dog receives a vaccination, it is important to keep a close eye on its behavior and general health. To help your pup feel more comfortable, try to keep your pet in a quiet, stress-free environment and offer them plenty of breaks to rest and relax. Additionally, it is important to follow the following steps:

Treat Any Allergic Reactions

If a dog experiences an allergic reaction after being vaccinated, it is important to contact your veterinarian immediately. Allergic reactions can range from mild to severe and can include symptoms such as hives, swelling of the face, vomiting, and difficulty breathing. It is important to monitor your dog closely after being vaccinated and to look for any changes in behavior.

If you notice any of the symptoms mentioned above, or if your dog seems to be unusually lethargic or irritable, it is important to contact your veterinarian right away. Treatment for allergic reactions may include antihistamines, steroids, and other medications.

Request Pain Relief Medicine

After a dog is vaccinated, it is common for them to experience pain and discomfort. To alleviate their discomfort, it is important to provide them with pain relief medicine as soon as possible. This will help reduce the pain and help the dog to adjust better to the vaccination. Pain relief medicine will also help to reduce the risk of any complications due to vaccination.

Additionally, it can help the dog to remain calm and relaxed during the recovery period. By providing the dog with pain relief medicine, you can ensure that they are feeling well and that their behavior changes are the result of the vaccination, rather than the pain.

Provide Relief If He Has a Fever

If your dog has a fever after a vaccination, it is important to take him to the vet for a checkup. In most cases, the fever is a sign that the body is fighting off the infection, and a simple fever reducer like acetaminophen or ibuprofen can provide relief. It is important to monitor your dog closely and make sure his temperature does not get too high.

If your dog’s temperature is over 104 degrees Fahrenheit, you should contact your vet right away. If the fever persists, the vet will likely want to run tests to determine the cause of the fever, which may include blood work or urinalysis. With proper care, your pup should make a full recovery and his behavior should return to normal soon.

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Provide the Space He Needs to Recover

After a dog receives a vaccination, it is important to provide them with the space and time they need to recover. Dogs may become lethargic, and may even experience some minor pain and discomfort.

It is important to avoid too much physical activity, or overstimulating activities, during this time, as it can lead to further stress on their body while they attempt to recover. Keeping their environment calm and quiet, and offering comforting cuddles and reassurance, is the best way to ensure they recover quickly and feel secure.

What Side Effects Can Dogs Get From Vaccines?

While dog vaccinations are essential for their overall health and well-being, they can sometimes cause side effects, just like any medication. It’s important to be aware of these potential side effects so you can monitor your dog and know when to call the vet.

Mild side effects are the most common and usually resolve on their own within a day or two. These can include:

  • Tenderness or swelling at the injection site: This is a normal reaction to the vaccine and usually goes away within a few days. You can apply a cold compress to the area to help reduce swelling and discomfort.
  • Lethargy or fatigue: Your dog may be less active than usual for a day or two after being vaccinated. This is because their body is working hard to build up immunity to the disease.
  • Loss of appetite: Some dogs may not want to eat as much as usual after being vaccinated. This is usually temporary and they should start eating normally again within a day or two.
  • Mild fever: A low-grade fever (up to 103°F) is a common side effect of vaccines and is usually nothing to worry about. However, if your dog’s fever is higher than 103°F or persists for more than a day, call your vet.

More serious side effects are rare, but they can occur. If you notice any of the following symptoms after your dog has been vaccinated, call your vet immediately:

  • Hives or itching: This could be a sign of an allergic reaction to the vaccine.
  • Facial swelling: This could be a sign of a serious allergic reaction called anaphylaxis.
  • Difficulty breathing: This could be a sign of an allergic reaction or another serious problem.
  • Vomiting or diarrhea: These can be signs of an allergic reaction or another gastrointestinal issue.
  • Seizures: These are a rare but serious side effect of some vaccines.

Dog Sick 4 Days After Vaccination

Here are some steps you can take:

1. Assess your dog’s symptoms:

  • What are the specific symptoms your dog is experiencing? Vomiting, diarrhea, loss of appetite, lethargy, fever, or other?
  • How severe are the symptoms? Are they mild and intermittent, or are they severe and persistent?
  • Are there any other concerning signs, like difficulty breathing, seizures, or facial swelling?

2. Consider the timeline:

  • Did your dog start experiencing these symptoms right after the vaccination, or did they appear later?
  • Have the symptoms been getting worse, or are they staying the same?

3. Contact your veterinarian:

  • It’s always best to err on the side of caution and consult your veterinarian when your dog is sick, especially after a recent vaccination.
  • Describe your dog’s symptoms and the timeline in detail.
  • Based on the information you provide, your vet will likely recommend bringing your dog in for an examination and possibly some tests to determine the cause of the illness.

4. Be prepared to answer questions:

  • Your vet will likely ask you questions about your dog’s recent activities, diet, and any other medications they might be taking.
  • Be as accurate and detailed as possible to help your vet make the best diagnosis.

5. Follow your vet’s instructions:

  • Depending on the diagnosis, your vet may recommend specific treatment for your dog’s illness.
  • It’s important to follow your vet’s instructions carefully to ensure your dog’s speedy recovery.

Dog Not Eating After Vaccination

It’s understandable to be concerned about your dog not eating after their vaccination. While a lack of appetite is a common side effect, it’s important to monitor the situation and take steps to ensure their well-being. Here’s what you can do:

1. Assess the severity and timeline:

  • How long has it been since your dog was vaccinated? If it’s only been a day or two, a decreased appetite is common and usually resolves within 48 hours.
  • Is your dog showing other symptoms like lethargy, vomiting, or diarrhea? These could indicate a more serious issue unrelated to the vaccine.
  • Is the lack of appetite complete, or are they eating very little? Complete refusal to eat is more concerning than a slight decrease in appetite.

2. Try tempting their appetite:

  • Offer their favorite foods or treats. Sometimes a change in flavor can entice them to eat.
  • Warm up their food slightly to enhance the aroma. This can make it more appealing.
  • Try hand-feeding them small, bite-sized pieces. This can be more engaging than leaving a full bowl.

3. Ensure hydration:

  • Make sure your dog has constant access to fresh, clean water.
  • Consider offering them water flavored with bone broth or tuna juice to encourage hydration.

4. Monitor and consult your veterinarian:

  • Keep an eye on your dog’s overall behavior and activity level. A significant decrease in energy could be a sign of something more serious.
  • If your dog hasn’t eaten anything for more than 24 hours, or if they show other concerning symptoms, contact your veterinarian immediately.

Do’s And Don’ts After Dog Vaccination

After your dog has received a vaccination, it is important to keep an eye on its behavior for the next few days. While most dogs won’t show any visible signs, some may be lethargic and have a loss of appetite. It is also not uncommon for them to be more sensitive to touch in the injection area.


  • Monitor your dog’s behavior, but don’t overreact if they seem a bit off
  • Provide plenty of comfortable bedding and rest time
  • Offer a warm meal if they have a decreased appetite
  • Keep your dog away from other animals until the vaccine has had time to take effect
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  • Don’t subject your dog to overly strenuous activities or extreme temperatures
  • Don’t bathe your dog for at least two days after vaccination
  • Don’t give your dog any human medications or supplements without consulting your vet
  • Don’t let your dog socialize with other dogs until after the vaccine has taken effect.

Debunking Myths: Separating Fact from Fiction About Dog Vaccines and Behavior

Myth 1: Vaccines Cause Permanent Behavioral Changes in Dogs

Fact: Vaccines may cause temporary behavioral changes in dogs as their immune system responds to the vaccination. However, these changes are typically short-lived and do not result in permanent alterations to their behavior. In most cases, dogs return to their normal selves within a few days.

Myth 2: Vaccines Can Make Dogs Aggressive

Fact: There is no scientific evidence to support the claim that vaccines directly cause aggression in dogs. While some dogs may exhibit temporary mood swings or irritability due to the immune response, these reactions are not the same as aggression. If your dog shows signs of aggressive behavior, it is essential to consult with a veterinarian or a certified behaviorist to identify and address the underlying cause.

Myth 3: Dogs Do Not Need Regular Vaccinations

Fact: Regular vaccinations are crucial for maintaining your dog’s health and preventing the spread of contagious diseases. While some vaccines provide long-lasting immunity, others may require booster shots to ensure continued protection. Consult with your veterinarian to determine the appropriate vaccination schedule for your dog based on their age, breed, and lifestyle.

Myth 4: Natural Immunity is Better Than Vaccination

Fact: While natural immunity can offer protection against certain diseases, relying solely on it can put your dog at risk for severe, sometimes life-threatening illnesses. Vaccination provides a safer, controlled way to stimulate your dog’s immune system without exposing them to the full-blown disease.

Myth 5: Vaccines Contain Harmful Ingredients That Can Cause Behavioral Issues

Fact: Vaccines are thoroughly tested and regulated to ensure their safety and effectiveness. The ingredients used in vaccines, such as adjuvants and preservatives, are present in small quantities and have been proven safe for use in animals. Any temporary behavioral changes experienced after vaccination are typically a result of the immune response, not the vaccine’s ingredients.

By debunking these common myths, you can make informed decisions about your dog’s vaccinations and better understand the connection between vaccines and behavior changes. Always consult with your veterinarian to address any concerns and ensure your dog receives the appropriate vaccinations for their overall health and well-being.


In conclusion, the behavior of dogs can change after vaccination, either positively or negatively. Vaccines help protect against many diseases, but can also cause side effects such as lethargy, loss of appetite, and changes in behavior. If you notice any behavioral changes in your dog after vaccination, it is important to contact your veterinarian to discuss these changes. With proper care and monitoring, your dog should eventually return to their normal behavior.


How long after a vaccine can a dog have side effects?

After a dog receives a vaccination, it is possible to observe side effects within a few hours to several days. Most common side effects, such as mild fever, lethargy, decreased appetite, or soreness at the injection site, typically occur within 24 to 72 hours after vaccination. These mild side effects usually resolve on their own within a few days.

How long does it take for a dog to feel better after a vaccination?

Most dogs will start to feel better within a day or two after receiving a vaccination. Mild side effects, such as lethargy or decreased appetite, usually resolve within 24 to 48 hours.
However, some dogs may experience more severe side effects or allergic reactions, which can take longer to resolve. It’s important to monitor your dog closely and contact your veterinarian if you notice any concerning symptoms.

Why is my dog aggressive after getting shots?

It is not uncommon for dogs to exhibit some changes in behavior or mood after receiving vaccinations, but aggression is not a typical or expected side effect of vaccinations. If your dog is exhibiting aggressive behavior after getting shots, it is possible that the behavior is related to something else entirely.
For example, your dog may be experiencing pain or discomfort at the injection site, which could make them more irritable or sensitive. Alternatively, your dog may be feeling anxious or stressed due to the visit to the veterinarian’s office, which can lead to behavioral changes.

How do you comfort a dog after a vaccination?

After a dog receives a vaccination, they may experience mild side effects such as lethargy, decreased appetite, or soreness at the injection site, which can be alleviated by providing a quiet and comfortable resting area, offering plenty of water, monitoring their appetite, applying a cold compress, and providing extra attention and affection. If there are any concerning symptoms or changes in behavior, it’s important to contact a veterinarian for guidance.

What breeds are more prone to vaccine reactions?

All dogs can potentially have an adverse reaction to a vaccine, but some breeds may be more prone to vaccine reactions than others. However, it’s important to note that individual dogs can have different reactions to vaccinations, regardless of breed.

Breeds that may be more prone to vaccine reactions include:
Miniature Schnauzers
Siberian Huskies

Can I bathe my dog 2 days after vaccination?

It is recommended to wait for at least two weeks after each vaccination before bathing your dog, especially if they are still on their vaccination schedule. This is because the immune system of puppies or young dogs is not fully developed, which can make them more vulnerable to infections as their body adjusts to the vaccine. By waiting a few weeks, you can help ensure that your dog’s immune system is fully activated and better able to protect them against potential pathogens.

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