Bioethics committees have issued guidelines that medical interventions should be permissible only in cases of clinically verifiable disease, deformity, or injury. Furthermore, once the existence of one or more of these requirements has been proven, the proposed therapeutic procedure must reasonably be expected to result in a net benefit to the patient. As an exception to this rule, some prophylactic interventions might be performed on individuals "in their best interests" or with the aim of averting an urgent and potentially calamitous public health danger. In order to invoke these exceptions, a stringent set of criteria must first be satisfied. Additionally, where the proposed prophylactic intervention is intended for children, who are unlikely to be able to provide a meaningfully informed consent, a heightened scrutiny of any such measures is required. We argue that children should not be subjected to prophylactic interventions "in their best interests" or for public health reasons when there exist effective and conservative alternative interventions, such as behavioural modification, that individuals could employ as competent adolescents or adults to avoid adverse health outcomes. Applying these criteria, we consider the specific examples of prophylactic mastectomy, immunisations, cosmetic ear surgery, and circumcision.