As such, a single exposure to the foreign agent may result in clinical symptoms. In both conditions, activation of mast cells results in a number of physiological changes affecting respiration and circulation which may present a life-threatening emergency. Snake or insect venom, the leptospirosis component or preservatives in canine vaccines, and antibiotics and other drugs are some of the common agents which can bring on anaphylaxis. Symptoms of anaphylaxis usually occur within one hour following exposure to the agent. Reaction may be restricted to the site of contact with the agent as seen with local swelling and redness associated with insect stings or may occur systemically in which the whole body will swell.
Dogs suffering from systemic anaphylaxis are usually restless and excitable.
Vomiting and bloody diarrhea, followed by collapse, convulsions, coma and eventually death indicate a state of anaphylactic shock secondary to systemic anaphylaxis. Systemic anaphylaxis constitutes a medical emergency. Circulatory collapse associated with anaphylaxis results in oxygen deprivation to major organs particularly the liver and gastrointestinal system. Fluid therapy to replace blood volume and epinephrine, which serves to increase blood flow as well as inactivate mast cell response, are the first course of treatment for anaphylaxis. Oxygen therapy may also be necessary.