Anaphylactic reactions to some chemotherapy drugs may occur within seconds or minutes if given intravenously. Anaphylactic shock is the most severe type of anaphylaxis, and is immediately life‐threatening. The most commonly used chemotherapy drugs associated with anaphylactoid effects are L‐asparaginase and doxorubicin. Anaphylaxis should be assumed and a veterninary patient (a dog or a cat) treated accordingly when the patient has a known risk factor (e.g., history of exposure to a drug associated with anaphylaxis), and is showing signs including restlessness, swollen face or legs, itchy head, urticaria vomiting/diarrhea, dyspnea, pallor or hypotension. The three important elements in the treatment of anaphylaxis are early recognition, airway maintenance, and hemodynamic support. Anaphylaxis is generally treated with fluid therapy (isotonic crystalloid and colloid) to maintain perfusion and blood pressure, as well as a combination of epinephrine, diphenhydramine (antihistamine), and a corticosteroid (dexamethasone, prednisone, methylprednisolone).