Anaphylactic shock is a serious, uncommon and exaggerated allergic reaction to some foreign substance that a dog comes into contact with,called an "allergen." If not treated quickly, anaphylactic shock can be fatal. Many things can cause anaphylaxis in dogs, depending upon the make-up of the particular dog’s immune system. These include drugs, flea and tick preventatives, venomous bites, oral or topical antibiotics, anesthetics, drugs prepared from animal products, diagnostic agents, mold, pollen and ingredients in food. An anaphylactic reaction usually happens suddenly, within moments after a dog touches, inhales, ingests or otherwise is exposed to the allergen. Without prompt treatment, anaphylactic shock almost always causes seizures, collapse, coma and/or death. Owners should always be aware of their dog’s behavior, so that they can take him or her to a veterinarian right away when something seems to be going wrong.