Hidden Valley Animal Clinic

100 Oakhurst Drive
McMurray, PA 15317



Vaccine Reaction

Immunizations (or vaccines) are intended to stimulate the immune system to protect the animal from the infectious agent. However, this stimulation may cause some minor symptoms. Your pet may react to immunizations in ways that range from soreness at the site of injection to mild fever to allergic reactions, which can range from mild to severe.

  • Mild. Mild reactions include fever, sluggishness, and loss of appetite. Mild reactions last about 24 hours and usually resolve without treatment.
  • Moderate. Hives and facial swelling - swelling and redness of the lips, around the eyes, and in muzzle. It is usually extremely itchy. This reaction usually develops 1-4 hours after the vaccine and can last several hours. Please refer to the section on facial swelling for treatment options.
  • Severe. The most severe reaction is anaphylaxis which is a sudden, severe allergic response that produces breathing difficulties, collapse and possible death. Symptoms usually include sudden onset of vomiting, diarrhea, staggering, pale gums, very low heart-rate, swelling of the larynx leading to airway obstruction (and inability to breathe), seizures and cardiovascular collapse or death. This reaction is life-threatening for your dog and must be treated immediately. These reactions usually begin within 15-20 minutes after the vaccine was administered.