Effect of aromatherapy on postoperative pain relief: A systematic review and meta-analysis of randomized controlled trials

•Postoperative pain and psychological distress are common problems.•This systematic review evaluated aromatherapy for postoperative pain.•The addition of aromatherapy to routine care significantly reduced postoperative pain.•Aromatherapy did not significantly reduce anxiety levels.•Certainty in the evidence was very low due to risk of bias, inconsistency, and imprecision.