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Dog Behavior Changes After Vaccination

It is important to vaccinate your dogs to keep them healthy and avoid diseases. Although vaccines are generally safe, some dogs may experience reactions to them. Our Madison veterinarians have provided information on the most common reactions to dog vaccines and what you should do if your dog reacts adversely.

Why should I get my dog vaccinated?

Ensuring that your dog receives its vaccines early in life and on a regular basis as an adult is crucial for its long-term health and well-being. Three common illnesses that can be fatal, especially in puppies, are rabies, hepatitis, and parvovirus.

It's always better to vaccinate your pet against these diseases instead of treating them after they have already manifested, which can be expensive and emotionally difficult.

Although the risk of your dog having a severe reaction to a vaccine is low, it's always important to consult with your veterinarian to determine the best course of action for your furry friend.

Does my dog need all the available vaccines?

Your veterinarian will assess the risks based on your dog's breed, age, and lifestyle, and then recommend the appropriate vaccinations.

What are the most common reactions to vaccines in dogs?

Adverse reactions are always a possibility with medical procedures, including vaccinations. Pet owners can be upset when they see how their beloved pet responds to vaccinations, but it's important to remember that the majority of reactions are mild and transient. It can be less stressful for both you and your dog to receive vaccinations if you are aware of the symptoms of a reaction and what to do if your dog exhibits them.


Dogs often experience lethargy and discomfort after receiving vaccinations, accompanied by a mild fever. This feeling can be described as being "off." It's a normal reaction, indicating that your dog's immune system is functioning well and responding appropriately to the vaccine. The symptoms are generally mild and should pass within a day or two. However, if your dog doesn't start feeling better within a few days, it's best to contact your veterinarian.

Lumps & Bumps

Lumps and bumps are common reactions to dog vaccinations, just like feeling 'off.' Following the vaccination, a small, firm bump may form where the needle was injected into the skin or muscle, leaving the area tender. These bumps form as a result of your dog's immune system rushing to resolve the localized irritation.

Sneezing & Cold-Like Symptoms

While most vaccines are administered via injection, the Bordetella bronchiseptica and parainfluenza virus vaccines are administered via drops or sprays into the dog's nose. Reactions to these vaccines can resemble a cold, with coughing, sneezing, and a runny nose. Most dogs recover from these symptoms within a day or two. If your dog develops more severe symptoms or does not recover within a few days, it is time to consult a veterinarian.

Serious Reactions To Vaccinations

While most dog vaccine reactions are mild and short-lived, our canine companions can have more severe reactions that require immediate medical attention in rare cases.

Anaphylaxis—This severe allergic reaction can involve facial swelling, diarrhea, itchiness, hives, vomiting, and breathing difficulties. It usually occurs very soon after your pet receives the injection (typically while you are still at the vet's office) but can happen up to 48 hours after the vaccine is given.

Shock - The symptoms of shock following vaccines can include a slow heart rate, decreased blood pressure, and generalized weakness. You may also see a gray tongue and pale mucous membranes.

Can I prevent my dog from reacting? 

Vaccines are important to safeguard your dog's long-term health, and the likelihood of your dog having a severe reaction to a vaccine is very low. However, if your dog has had a previous reaction to a vaccine, it is crucial to inform your veterinarian. Your vet may advise you to skip a specific vaccination in the future. 

When multiple vaccinations are given in a single visit, there is a slightly higher risk of adverse reactions to vaccinations. Smaller dogs may be particularly prone to this. Your veterinarian might suggest spreading out your dog's vaccinations over a few days instead of all at once as a way to lower the risk of adverse reactions.

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.

To learn more about vaccinations and preventive healthcare for your dog, contact our Madison vets today to book an appointment.

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