Administering vaccines is at the core of the services we provide at Carolina Value Pet Care, yet there are occasions when a pet may have a reaction to a vaccine.  Fortunately for you and your pets, we use the highest quality vaccines in the pet industry, so we seldom see a reaction to a vaccine.  And we NEVER have the expectation of a vaccine reaction, even in the more susceptible breeds.  But the question of reactions does come up, so let’s address how vaccine reactions may show up in a pet, and what to do if it does happen.

Of the vaccines we give to Dogs, the 2 most common vaccines responsible for a reaction are 1) Rabies and 2) Leptospirosis.  For Cats, the most common cause of a reaction is Feline Leukemia.  To emphasize again, while vaccine reactions may occur, they are very uncommon.  However, some Dog breeds are more likely to exhibit a reaction than other breeds:  Dachshunds, Schnauzers, Pugs, Boston Terriers and Chihuahuas lead the list.  In general, the smaller the breed, the more likely they are to react.

There are 3 ways that vaccines may cause an adverse, and each one is managed differently when they occur.

  1. Pain at the injection site, which may also result in lethargy or sluggishness
  2. Intestinal upset, which may result in vomiting and/or diarrhea
  3. Swelling of the face, lips, around the eyes and hives (multiple bumps on the skin)

1) PAIN in DOGS:  The most common vaccine reaction in pets (and in people, too) is pain at the injection site.  While it’s unusual for any pain or lethargy to last more than a day, we can help provide relief from any discomfort with the use of Aspirin (NOT Tylenol !).  We recommend using Children’s Aspirin for smaller dogs. The dose is:

* CHILDREN’S ASPIRIN (81 mg):  Give 1 Children’s Aspirin for every 15 lbs of body weight.  You can give it by mouth every 12 hours as needed.  If you have a very small dog (say, 5 lbs), you can give ½ of a Children’s Aspirin, although you may need a pill-splitter to cut them safely.

You can also try to apply a warm compress to the injection site, although most dogs won’t sit still long enough for it to help.  Still, it’s worth a try.

2) INTESTINAL UPSET in DOGS:  We don’t see dogs with intestinal upset very often following vaccines.  And I suspect that in many cases any vomiting and/or diarrhea may result from anxiety (the car ride … the presence of other dogs, especially if there is a lot of commotion … in general, just being out of their comfort zone) more than the vaccines.  Pepto-Bismol liquid (not tablets) (and generic Pepto is OK) can be extremely helpful to settle down nervous and upset stomachs.  The dose is:

* PEPTO-BISMOL: Give 1 teaspoon for every 10 lbs of body weight.  You can give it every 6 to 8 hours as needed, but be patient for it to work.  If your dog has spit up, then avoid giving any food for at least 12 hours.  And resume feeding with a smaller–than–usual meal.  Pepto will often make the stools look darker or even black.  This is normal. 

3) SWELLING of the FACE, LIPS, EARS, Around the EYES, with or without HIVES (multiple bumps on the body):  This is most visually frightening reaction to a vaccine, and it needs to be addressed as soon as possible.  The swelling may be subtle or it may be significant.  And it may occur in a few minutes after giving a vaccine … or it may occur a few hours later, but most of the time, swelling will be present within 30 minutes of receiving vaccines.  These are true “reactors” and we need to know if your dog has ever had this type of reaction before we give any vaccine so we can give a medication prior to vaccinating  her/him to greatly reduce the likelihood of a severe reaction.  Fortunately, giving Benadryl can help these reactors.  And when these dogs are presented to us, we will alsogive a cortisone injection.  The dose of Benadryl:

* CHILDREN’S CHEWABLE BENADRYL (Generic is OK):  Give 1 chewable tablet for every 10-15 lbs of weight.  Give every 6 to 8 hours as needed.  It will take a WHILE for the swelling to go down.

You can also give liquid Benadryl, but dogs do not generally like the taste. 

* CHILDREN’S LIQUID BENADRYL:  Give 1 teaspoon for every 10-15 lbs of body weight.   Give every 6 to 8 hours as needed.  It will take a WHILE for the swelling to go down.

As mentioned earlier, smaller breeds are more likely to have an adverse vaccine reaction.  But remember that reactions are uncommon !  Unfortunately, we do encounter ill-informed and misguided breeders who use scare tactics about vaccine reactions to new puppy parents.  Consequently, many puppies are not getting vaccines as they should, especially at the most critical phase of their development.  The risk of exposure to potentially life-threatening viruses we can protect against may be far greater than the risk of a vaccine reaction.    


While it is even less common for cats to have a reaction to a vaccine than dogs, we have to be more careful how we manage pain and lethargy when it does occur.  Unfortunately, medications such as Aspirin and Tylenol can be extremely dangerous to cats, so DO NOT USE Aspirin or Tylenol !  If you kitty is experiencing pain or discomfort or lethargy for more than 12 hours, we recommend seeing a full-service veterinarian to provide pain relief. 

Intestinal upset is very uncommon to see. And it is extremely rare to see a cat exhibit swelling of the face, eyes, etc following a vaccine.  

We truly hope you never have to experience any side-effects with your pets to ANY vaccine or medication that we offer.  But if you have any further questions, you may contact us Mon-Fri from 8:00 am-5:00 pm at 704.288.8620.                                                                        

Dr Bob Parrish