Signs Your Dog Is Having A Vaccine Reaction

Vaccinating your dog is an important part of being a responsible pet owner, but so is educating yourself on the care and keeping of your furry companion. While some aspects of long term care – monthly flea treatments or heartworm pills, for example – can be safely and easily taken care of at home, vaccines are often a bit of a mystery to new pet owners. That doesn’t mean that owners should be scared or hesitant about getting them, but rather that they should research vaccines and feel confident that they know what to do post-appointment in order to avoid some type of dog reaction to a vaccine.

Just like vaccines in human children, there are concerns and debates about many aspects of vaccination for pets, but don’t let this keep you from doing the right thing for your four-legged friend. Vaccines are as important as regular checkups, a healthy diet, exercise, and affection for your pooch. In addition to protecting your dog’s health and overall well-being, learning how to recognize potential vaccine reactions will help put your mind at ease. This article will discuss how to spot a dog vaccine reaction, as well as important information every pet owner should know about the vaccination process.

How To Determine If Your Dog Is Having A Vaccination Reaction: 7 Questions To Ask

Before you get worried about your dog, keep calm and objectively examine any potential symptoms, even if you really think the vaccine must be causing them. It’s common for pet parents to get so worked up convincing themselves that a vaccine will hurt their dog that they misattribute symptoms (or even identify some that aren’t really there). Ask yourself these seven crucial questions to determine if your pet is having a vaccine reaction:

  • How long ago did your dog have his vaccination? According to the American Medical Veterinary Association, nearly all of the expected, non-serious injection or administration symptoms of pet vaccines will arise and fade away within a week. If a problem is cropping up multiple weeks or months later, there’s very little chance it has anything to do with your dog’s previous vaccination. The notable exception is a small swelling or knot under the skin in the case of an injected vaccine, which is normal and may last up to three weeks after vaccination. Because of the precautions taken in a veterinary office – sterilization, clean instruments, gloves, and so on – your pet is as safe in their hands as you are in your doctor’s while getting a vaccine.
  • Did he have any underlying health problems during the vaccination process? Because there are a lot of misunderstandings and misconceptions about vaccines in both the human and animal world, they make a convenient scapegoat for any health problems that show up. While vaccines can and do exacerbate certain health conditions, such as environmental and pollen allergies in some dogs, they aren’t necessarily to blame for every limp, dry skin ‘hot spot’, or behavioral issue your pet suddenly seems to have. In other words, correlation is not causation, and speak to your vet to rule out any serious issues before blaming a vaccine for symptoms.
  • Does anything seem to help the symptoms? Most pet owners have their go-to remedies for soothing their furry companion – a special spot at the foot of the bed if they’re spooked by fireworks, or a favorite blanket if they’re feeling cold can go a long way to making your dog feel well-adjusted again. If the ‘usual remedies’ appear to erase the worrisome symptoms, chances are it’s simply a health or behavioral problem that happened around the same time as the vaccine, not one biologically caused by it. Of course, if the symptoms are immediately serious or life-threatening – such as shaking, collapsing, uncharacteristic canine aggression, visible wounds or scabbing of the skin, complete lack of  appetite in your dog – the AMVA recommends making a vet appointment right away for an in-depth assessment.
  • Is your pet eating and drinking? Speaking of appetite, that’s one of the first signs that something is wrong with your dog, whether it be a vaccination reaction or other illness. In the wild, animals have to carefully balance the energy they expend hunting, consuming, and digesting food with the energy needed to heal themselves from an injury or sickness. That natural instinct is alive and well in domestic pets, so you’ll probably notice they have a little less “pep in their step” for a day or two after a vaccination – remember, they don’t know that the vaccine is helping them, they just know they don’t feel well. If, however, you don’t notice your dog trying to eat or drink at all by the end of the day after their vaccination, it could be a sign something is wrong.
  • Is your pet eliminating? Just as it’s important to make sure things are going into your pet, you should make sure things are coming out of him as well. Some normal vaccine reactions can cause a little constipation in dogs or short-term, non-serious canine diarrhea as their bodies adjust. If you notice discoloration or blood in your dog’s urine or stools, however, that’s a red flag that should be investigated by a medical professional. This is reasonably easy to detect by paying close attention when you’re taking your dog on a walk.

Helpful Hint: It may seem a little gross, but snapping a clear, well-lit picture with your smartphone of any problematic urine or bowel movements can be a very beneficial tool at your vet’s office. Remember, it’s for your pet’s health and you can always delete it later!

  • Is your pet vomiting? In general, vomiting is more common in animals than humans –dogs will purposely eat grass to induce vomiting if they’re feeling sick to their stomach. Allergens, foreign objects, bad tastes, and potentially harmful substances can all result in one of those unpleasant surprises on the living room carpet. Vomit itself isn’t cause for concern, but rather uncontrolled, sustained, and violent vomiting – such as your pet struggling to breathe as they vomit. The appearance and timing of your dog vomiting is another clue for vaccine linkage – if they got sick immediately after eating a new food or table scraps, it might be the food at fault, rather than their previous trip to the vet’s. This is another case where it’s a good idea, if a bit nauseating, to snap a picture to show your vet later.
  • Is there swelling around their face, nose, or mouth? Histamine reactions are one of the first and most visible pet vaccine reactions, and thankfully they tend to happen while still in the vet’s office. If you notice prominent swelling in your pet, such as difficulty breathing in your dog, directly after their vaccine visit, get in touch with your vet and ask to bring your dog back in right away for examination. They may be allergic to some or all of the components in the vaccine and will need to be treated for severe allergic reaction. If this ends up being the case, consider getting a medical alert tag for their collar to prevent the issue from happening in the future.

How To Approach Dog Vaccine Reactions

While vaccine reactions happen, even in some healthy dogs, they are almost always because of an underlying or existing health issue in the animal, not the vaccine itself. Blaming the vaccine instead of getting to the root cause of the symptom could cost your pet valuable time, and potentially complicate their path to recovery, even if you mean well. Leaving a pet unvaccinated is a huge risk, and could cost them their life if they’re exposed to a virus like parvo or canine rabies. Below, some useful guidelines to keep in mind when vaccinating your pet:

  • Trust your vet or medical professional: No human being is infallible, but veterinarians and their support staff have all been trained and supervised by experts in their field of medicine. They want your pup to be healthy just as much as you do, and they wouldn’t put them in harm’s way. After all, a vet office that constantly made healthy pets sick wouldn’t be in business very long! If you have questions or concerns, bring them up to your vet before the vaccination. If their “bedside manner” still makes you feel nervous about taking your pet there, try visiting a different vet office – just don’t put off the vaccination.

For routine vaccinations, you can also get in contact with your local rescue shelter or ASPCA-like organization. These groups typically hold or can direct you to vaccination and spay/neuter fairs for low cost, quickly administered vaccines outside of a traditional office. This is a great alternative choice for dogs that may get nervous or stressed out when visiting the vet’s office, though they will still need to either be in a carrier or restrained for the safety of everyone at the pet care event.

  • Don’t over-vaccinate: Vaccines are an excellent tool in safeguarding canine health, but they can’t simply be administered over and over. There are time periods during which a vaccine is considered effective and active in your pet, and during that time your dog should not receive that same vaccine again. A rabies vaccine for dogs is an excellent example of this concept – once your puppy has gotten their initial shot and the one year booster that comes after it, they generally only need a new rabies shot every three years.

If you were to get them a new rabies shot every year, they could experience serious complications, including injury and even death. Vaccines are balanced and administered in accordance with your dog’s age and weight, formulated to remain in the body for a specific amount of time. Adding more vaccine than your pet’s body can safely handle could affect the immunity in a negative way.

  • Listen carefully to post-vaccination instructions: Depending on the type of vaccine and the administration method used – inhalation versus injection, for example – your vet may have different care instructions. Everything from breed to age of an animal will affect how they react after a vaccine, so this after-visit care is crucial to follow to the letter.

If you have a partner or a family member that will be watching your dog after their vaccination, make sure they’re made aware of these instructions too. It’s important that everyone in your dog’s family feels empowered to help them heal and has the tools to save their life if something goes wrong. Putting instructions on the front of your fridge is an excellent, high-visibility practice for important pet care information.

  • Keep contact information handy: If an emergency vaccine reaction occurs with your dog, the last thing you’ll want to be doing is frantically searching for your vet’s number. Get a card or magnet from your vet’s office, put their number in your cell phone, and get the name and number of the nearest 24-hour vet facility in the area. This information is important to have on hand for dog sitters anyway, so you’ll be taking care of two to-do list items at once. If you are travelling with your pet or staying in an unfamiliar place, a local pet rescue organization should be able to provide you with names, numbers, and hours of local vet offices.
  • Be honest about your dog’s medical history: If you’ve previously skipped vaccinations or been a little less than diligent about yearly check-ups, it’s far more important to be honest with your vet than tell a white lie or two. They aren’t in business to judge you, but they do need to know if there’s a chance that stray you brought in a few months ago might have already been vaccinated by a well-meaning person. Over-vaccination could be a very real threat if a new dog or cat has recently joined your household from parts unknown.


Your dog is a much-loved member of your family, and that’s why they deserve the best medical care that you’re able to offer them. Vaccines are safe, effective, and readily available for dogs and cats, and it doesn’t take much expertise to stay vigilant about vaccine reactions. When in doubt, document, photograph, and contact your vet’s office for guidance – it’s the best thing you can do for your pet and your peace of mind.



  1. “What to Expect After Your Pet’s Vaccination.” (American Veterinary Medical Association), (no publish date, 2018), Accessed November 27, 2018.
  2. Dilmore, DVM, Dr. David. “Why do some pets get vaccine reactions?” (Banfield Pet Hospital), (no publish date), Accessed November 27, 2018.
  3. “Parvo in Dogs.”, (no publish date), Accessed November 27, 2018.

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