One stick of sugar-free peppermint-flavoured chewing gum (Wrigley’s Extra Sugarfree Gum, Wrigley Company) in the event of nausea, retching and/or vomiting occurring in the post anaesthesia care unit (PACU) after anaesthesia. Patients will be observed by a blinded observer who is a member of the study team. While in the PACU patients may spontaneously report nausea or be observed to retch or vomit. If patients do not spontaneously report nausea and are not observed to retch or vomit, they will be asked “Are you feeling sick?” every 15 minutes by the observer. If nausea, retching and/or vomiting are present the patient will be assessed for alertness using the Observer’s Assessment of Alertness and Sedation (OAA/S) score. If the score is 5, the observer will leave the PACU, maintaining blinding to group allocation. The PACU nurse will then randomize the patient and administer the randomly allocated intervention. Fifteen minutes later, the chewing gum will be discarded (if applicable). The blinded observer will then return to the PACU to observe the patient continuously for retching or vomiting and to ask about nausea every 15 minutes until 2 hours after randomization. Rescue medication will be administered to patients who experienced a nausea score of moderate or severe for a period of >15 minutes, 2 or more episodes of retching or vomiting within 15 minutes, at patient request or at the discretion of the treating team any time from the administration of the randomised treatment to 2 hours later. The observer will be blind to the identity of each rescue medication given. Patients will be discharged from the PACU when they meet local discharge criteria. If the OAA/S score is <5, chewing gum will not be allowed. The patient will receive anti-emetic treatment at the discretion of the attending anaesthetist and will not be followed further. The number of consented patients who are not randomised will be reported, with reasons. Patients who are randomised to chewing gum but who do not chew it (for whatever reason) will receive ondansetron 4 mg IV (the first rescue treatment in the chewing gum group) and will continue in the study as part of the chewing gum intention-to-treat arm.