Get

In Your Inbox

Dogster is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

Vaccine Reactions in Dogs: Our Vet Explains the Signs and How to React

Vet extracting blood from a maltese

Many people are hesitant and wary to vaccinate their dogs because they are worried about vaccine reactions. When people think of vaccine reactions, many assume the worst in that their dogs will develop a debilitating disease or just immediately pass away. Luckily vaccine reactions are rare in our pet dogs as vaccines have been studied, created, and improved over years and years of research. However, as with anything that goes in or onto your dog’s body, reactions can still occur. Keep reading to learn more about vaccine reactions in dogs, what to look for, and what to do if you think your dog is having a reaction.

Dogster divider_v2_NEW_MAY_24_

What Is a Vaccine Reaction?

In dogs, when a veterinarian refers to a “vaccine reaction”, they are referring to an adverse effect the vaccine has caused to your dog’s body. These reactions occur because your dog’s immune system is doing its job. In other words, your dog’s immune system is responding by launching a response in the body, though sometimes this can go into overdrive.

Most commonly in dogs we are going to see mild reactions that will only last for a few hours. Vaccine reactions may occur immediately (within minutes) or hours to, rarely, a few days later. Dogs do not tend to develop long-term vaccine reactions that we can sometimes see in cats or people. Contrary to conspiracy theories in people, vaccines do not cause long-term effects such as autism, stunted growth, developmental disorders, or behavioral issues in dogs.

vet-giving-injection-to-dog
Image Credit: Leoschka, Shutterstock

What Are the Signs of a Vaccine Reaction in Dogs?

There are different types of vaccine reactions. What most people think of is actually very rare, which is an anaphylactic reaction. Anaphylaxis typically occurs within minutes of receiving a vaccine. Anaphylaxis typically causes collapse, vomiting, pale gums, heavy breathing, diarrhea and then swelling/redness of the body.

More commonly in dogs we will see vaccine reactions occur within minutes to hours later. Commonly we will see hives, redness, itching, and mild swelling. Sometimes there will be tenderness at the vaccine site and a mild fever associated with inflammation (not infectious in nature). The hives and redness may just be around the vaccine site, or affecting the entire body. It’s not uncommon for a dog to get a puffy face, even if the vaccine was given in the back leg. If a mild fever is seen, your dog may experience mild lethargy, or the body temperature is found to be slightly elevated with a thermometer.  It’s an old wives’ tale that a fever has anything to do with how your dog’s nose feels (e.g., wet, dry, cold, warm).

If your dog had an oral or intranasal vaccine, you may notice mild sneezing, coughing, reverse sneezing, rubbing the face, and/or mild gagging. Typically, these will resolve within a few minutes to hours after getting the vaccine.

What Are the Causes of a Vaccine Reaction?

Most commonly, vaccine reactions occur because your dog’s body is mounting an overzealous immune response to the vaccine. The immune system may cause inflammation, leading to a mild fever and lethargy. Other times components in the vaccines may cause a mild allergic reaction to occur. This is when we may see the puffiness, redness, hives, and/or swelling over the body.

The actual injection itself can also cause mild inflammation, swelling, and irritation at the injection site. Just as you may get redness and bruising after you have blood drawn, your dog’s body can react the same way from a needle poke. This can be made worse by a dog who is excited, anxious, and/or difficult to handle at the veterinarian as excess movement may cause the injection to be more traumatic

Beagle dog biting his itching skin on legs
Image Credit: Przemek Iciak, Shutterstock

How Do I Care for a Dog With a Vaccine Reaction?

First, if you leave the hospital with your dog or puppy breathing fast after vaccination and/or they vomit, collapse, become acutely lethargic, and/or non-responsive, you need to immediately bring them back to the hospital. Anaphylactic reactions, while rare, can be deadly. They can cause a dangerous drop in blood pressure, poor circulation, and generalized inflammation. Immediate care with fluids and aggressive medications may be needed to stabilize your pet. If caught and treated immediately, dogs tend to do well.

If your dog develops mild signs – such as injection site swelling, soreness, hives, itching, and/or a mild puffy face – then contact a veterinarian. A veterinarian may just have you administer an antihistamine by mouth at home, dosed based on your dog’s weight. The veterinarian may also want you to come back with your dog to the hospital so that they can give injectable antihistamines and/or steroids.

Never administer Aspirin, Ibuprofen, or any other OTC products to your dog unless specifically directed by a veterinarian. While the veterinarian may want you to give an antihistamine, any OTC pain and anti-inflammatory products may be harmful to your dog. Always consult with a veterinarian’s office first to determine a plan that is right for your pup.

Did you know you can speak to a veterinarian without having to travel? Just head over to PangoVet. It's our online service where you can talk to a vet online and get the advice you need for your pet — all at an affordable price!

PangoVet_Mention-in-Content Savings V1

Dogster divider_v2_NEW_MAY_24_

Frequently Asked Questions (FAQ)

My Dog Had a Vaccine Reaction Once, Will it Occur Again?

Not necessarily. Your dog may have the same vaccines for years, and then suddenly develop a reaction. Or, vice versa. Your dog may have a history of reactions, and then do fine. Most veterinarians will do pre-medications with Diphenhydramine +/- steroids if a dog has a history of a vaccine reaction in the past.

Can I Split up Vaccines to Decrease Reaction Rates?

Some owners and veterinarians prefer to split up the dates that they administer vaccines, especially in small dogs and/or dogs who have had reactions in the past. The hope is that by separating vaccines by a few days or even a few weeks, the body won’t be overwhelmed with mounting a response to multiple vaccines at the same time. This is a completely acceptable practice as long as you and the veterinarian are still following appropriate guidelines to keep your dog protected and safe.

Why Do I Need to Have My Dog Vaccinated?

This is a subject for an entirely different article. But the short answer is that many of our vaccines are lifesavers, and can prevent fatal disease. Rabies when contracted is 100% fatal. A vaccine is much safer than your dog getting bit by a bat or a stray or wild rabid animal. Vaccines against parvovirus and distemper also help to prevent these diseases which at minimum will cause significant health problems and are also frequently fatal. Vaccine recommendations have been revamped over the years and we now know our dogs do not need to be vaccinated for certain things yearly, decreasing the chance of reaction. Speak with a veterinarian about appropriate time tables based on your dogs’ age and lifestyle.

dog getting injected at the veterinary clinic
Image Credit: Ground Picture, Shutterstock

Dogster divider_v2_NEW_MAY_24_

Conclusion

Vaccine reactions can manifest in many ways in our dogs, but most frequently they will be mild and self-limiting. Most commonly we will see an over-active immune response to a vaccine cause redness, hives, swelling, or even a low-grade fever. Soreness and swelling at the injection site are common, especially if your dog is rambunctious at the vet. Anaphylactic reactions, the most severe kind of vaccine reaction, is rare. However, if this occurs, your dog should be seen immediately by a veterinarian for care.

Vaccines help to prevent many fatal diseases, and are recommended in all of our pet dogs. However, the exact timetable and recommended vaccines should be discussed with a veterinarian to determine what is best for your pup. Treating mild vaccine reactions with OTC antihistamines may be appropriate, and many dogs will even be pre-treated if they have had reactions in the past.

Our vaccines and recommended protocols have made significant strides over the years. I encourage you to speak with a veterinarian about the best, most up to date and educated research into what is best for your dog rather than reading about rare horror stories on the internet. Vaccines truly do save lives and the risk of reactions is better than a certain death by disease.


Featured Image Credit: Lucky Business, Shutterstock

Want content like this delivered to you?

Sign Up For Our Newsletter

News, insights, expert advice, and everything dog

* By submitting, you agree to our Terms & Conditions and Privacy & Cookies Policy.


How useful was this post?

Click on a star to rate (you can leave written feedback after clicking submit)

Help us improve Dogster for pet parents!

Your feedback really matters.

What did you like about this post? Also how can we improve it?

Join the conversation

Leave a Reply

You’re very welcome to leave a comment or question. Please know that all comments must meet our community guidelines, and your email address will NOT be published. Let’s have a positive and constructive conversation.


Talk With A Vet Online

Peace of mind,
anywhere, anytime

Affordable vet advice

Why Does My Dog Pee Next to the Pad? 7 Vet-Reviewed Reasons

Using puppy pads is a convenient way to potty train a puppy, especially if you’ve got a smaller dog breed that has to...

Sheltie vs Collie: Differences Explained (With Pictures)

Shelties and Collies are intelligent and loving dogs that have captured the hearts of dog lovers worldwide. While they share some similarities, such...

Sharp Eagle (Shar-Pei & Beagle Mix) Dog Breed: Info, Pictures, Care & More

Sharp Eagles are not a type of eagle, but you probably already know that. They are a mix of two purebred dogs: the...

How to Show Love to Your Dog: 10 Affectionate Ways

Are you new to owning a dog? Or maybe you’ve had a furry friend for a while and are looking for different ways...

More related

Meet Rosa & Machado, Our Adorably Cheeky Rescue Pups

Welcome to the Wednesday Dogs of Dogster! Every Wednesday, we share a story from one of our Dogsters. This week is about Nicole...

Labrador Retriever Puppies for Sale in Mississippi: Breeders List 2026

Potential pet parents look for several appealing traits when searching for a canine companion. While some might prioritize a dog’s looks over performance,...

19 Dog Breeds Similar to Labradors (With Info & Pictures)

Labradors are the most beloved dogs in America (and have been since 1991), and for good reason; the breed is sociable, loyal, fun,...

Why Dogs Lick Everything? 9 Reasons & How to Stop It

Regardless of your dog’s breed or age, it’s unlikely that you’ll be able to avoid all the licking. Dogs are well known for...

Keep reading

Victor Dog Food vs Blue Buffalo 2026 Comparison: Pros & Cons

When it comes to choosing food for your dog, it can be confusing and difficult to choose between brands. We all want the best for our dogs, but it’s not uncommon to unintentionally select a food that isn’t appropriate for...

Dogster_Dog Food Victor VS Blue Buffalo

9 Best Puppy Foods for Small Breeds in 2026 – Reviews & Top Picks

Small dogs may think they are big and intimidating, but their nutritional needs are unique. Small breeds have smaller stomachs and higher metabolisms, so they need nutrient-dense formulas to ensure adequate nutrition without weight gain. Finding the appropriate food for...

jack russell terier puppy eating food from bowl

Is There Horse Meat in Dog Food? Separating Truth From Fiction

There is a great deal of information floating around about dog food and its ingredients, and it can certainly be difficult to tell facts from fiction. For example, you may have heard that there is horse meat in dog food....

Fresh horse meat on a platter

Can Dogs Be Vegetarian? Vet-Verified Nutrition & Health Facts

Dogs are considered omnivores, or facultative carnivores, meaning they can digest and utilize both animal and plant-based foods in their diet. However, did you know dogs can be fed a vegetarian diet and thrive? Dogs do not need meat in...

The dog sits near a bowl of food and licks his tongue, dry food and fresh vegetables and fruits

Can Dogs Eat Longan? Vet-Verified Nutrition Facts & FAQ

For humans, few fruits match the burst of musky sweetness that a longan fruit offers, but can dogs eat longan? Dogs can eat a small amount of longan, providing the shell and pit of the fruit are removed. However, just...

Can Dogs Eat Longan

8 Best Dog Foods for Boston Terriers in 2026 – Reviews & Top Picks

Boston Terriers are affectionate and loving dogs that make wonderful family pets. Their tuxedo black-and-white markings have given them the nickname the “American Gentleman.” If you own one of these dogs, you know how amazing they are and you want...

boston terrier dog eating from white bowl

What Is Fish Meal in Dog Food? Vet-Approved Safety Facts & FAQ

If you’re a dog owner who likes to read pet food labels, you’ll probably find quite a few unfamiliar ingredients listed. One such product is fish meal, commonly found in allergy-friendly diets. But what is fish meal in dog food,...

Wet and dry pet food made of natural ingredients

Can Dogs Eat Gingerbread? Vet-Verified Nutrition Facts & Safety Guide

Gingerbread is a holiday staple many people enjoy for the flavor and nostalgia. While dogs can eat certain holiday foods safely, it’s not recommended for dogs to eat gingerbread or gingerbread cookies. Small amounts of ginger may be okay for...

Can Dogs Eat Gingerbread