Perioperative anaphylactic as well as anaphylactoid reactions can be elicited by drugs, diagnostic agents, antiseptics, disinfectants and latex. In some individuals, allergic reactions occur in the absence of any evident risk factor. Previous history of specific safe exposure to a product does not permit to exclude the risk of having a reaction. We have systematically reviewed characteristics in the patient's history or clinical parameters that affect the risk of developing reactions during anesthesia. Evidence shows that patients with previous unexplained reaction during anesthesia are at risk for perioperative allergic reactions. An allergic reaction to an agent is associated with previous reaction to a product that is related with the culprit agent. Multiple surgery procedures, professional exposure to latex and allergy to fruit are associated with an increased frequency of latex allergy. It has been shown that in some instances, allergic perioperative reactions may be more common in atopic patients and in females.