by Rachael Joseph

Created on: August 22, 2009   Last Updated: August 23, 2009

Allergic Reactions to Vaccines

Allergic reactions to vaccines are one of the most common things we treat in the veterinary emergency room, ranging from mild to severe. If you know your pet has a history of vaccine reactions, please notify your veterinarian first. Another popular method of vaccinating is staggering, or giving a different vaccination each year. For example, year one your dog will get a full exam and three year rabies vaccine. Year two, your dog will get a full exam and DHPP vaccine. Year three, your dog will get a full exam and Lyme vaccine if you live in an at-risk area. Another popular choice for year three is the leptospirosis vaccine. This ensures your pet will get a full physical examination each year which is extremely important (and should be every six months for geriatric animals) and if your pet does have an allergic reaction, by breaking up the vaccines, your veterinarian is much more likely to know which vaccine is causing the allergic reaction.

Signs of a vaccine reaction usually include facial swelling, hives, and vomiting. Call your emergency clinic or regular clinic as they may want you to give your pet a benadryl dosage at home before returning to the clinic. Be sure to call the clinic for proper dosing information. Upon arrival at the clinic, your pet may be displaying any of the above mentioned symptoms or wheezing and/or difficulty breathing. Your emergency clinic will typically give a highly concentrated benadryl (diphenhydramine) injection and another injection, either epinephrine or a fast-acting steroid will be given. Your pet may also require fluid and oxygen therapy until the symptoms of the vaccine reaction have subsided.

Rarely and at the worst case scenario, your veterinarian may not be able to stop the reaction. If the reaction cannot be stopped, the pet may die or the liver can be greatly damaged. The liver is the primary organ affected by the shock vaccine reaction causes. When the body is deprived of oxygen during a reaction, the liver, stomach and intestines can all be deprived of oxygen. This can lead to ulcers or another condition called DIC (disseminated intravascular coagulation) where the pet's blood is unable to clot. Without clotting, hemorrhages can occur throughout the body and it can be fatal. DIC is most often treated with transfusions of fresh frozen plasma.

These worst case scenarios however, are exactly that. They are rarely seen and swelling of the face and hives are most commonly seen. Either way, better safe than sorry is a cliche that holds true when it comes to vaccine reactions in all pets.

Learn more about this author, Rachael Joseph.
Click here to send this author comments or questions.