Vaccine reactions in dogs
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Vaccinations work by stimulating the immune system in your dog by mimicking a 'real' virus or bacteria attack. Your dog's immune system then generates antibodies which act to protect him from catching it in the future. Whilst most vaccinations are carried out without event with only minor discomfort, some dogs can react violently to vaccinations and until it happens, you can't pick which dog will react and which won't.
Vaccination reactions range from mild reactions which typically result in a sleepier dog, sometimes with local redness or swelling at the vaccination point. These usually resolve after 24-48 hours and you don't need to do too much except to make sure your dog is comfortable and warm.
More serious reactions result in wheals forming in the skin of the dog. This usually occurs within the first hour or so after the vaccination and typically you'll notice swelling around the face and lips - for some it's so bad they can't even open their eyes. It is also usually extremely itchy for your dog. This can proceed to the more serious anaphylactic reaction where the dog experiences breathing difficulties, seizures, vomiting and/or collapses. Anaphylaxis is potentially fatal and needs to be looked at immediately. Most dogs who do have anaphylactic reactions to vaccinations do so within the first hour of exposure so thankfully, these when they do occur do tend to happen at the clinic where the vaccinations are taking place and therefore can be attended to quickly by the veterinarian.
Both anaphylaxis and urticaria are reactions that are triggered by antibodies that the immune system has made to some portion of the vaccine and usually requires at least one previous exposure to the vaccine. The antibodies cause inflammatory cells like basophils and mast cells to release substances that cause the allergic reaction. The impact on the dog may be life threatening but if treated successfully the prognosis for long-term health is good. Mild reactions usually resolve without treatment.
Having said that, the risks of a dog having adverse reactions to vaccinations aren't very common and the benefits of having a vaccinated pet protected from potentially fatal diseases far outweighs the risk which is why most veterinarians will advise the vaccinations of all dogs.
I would suggest however that you schedule your veterinary visit so that you can monitor your dog after the vaccination to ensure that you will pick up on any untoward effects of the vaccination.
There have been some reports of some dogs who have local reactions to vaccines which result in a lump in the area - seems to happen more often with the rabies vaccine. These lumps can take up to 2 months to resolve and most times don't cause the animal any pain or discomfort. For some dogs these lumps don't seem to resolve and can last for longer than that - if that is the case, visit your veterinarian to discuss your options which may involve surgical removal of the lump.
If your dog has a history of reactions to vaccines, let your veterinarian know so that he/she knows not to administer them again the next time.
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