The human body has unique electrical characteristics. These characteristics have been investigated in various studies in human-computer interaction (HCI) and related research fields. Such studies include applications for using the body as a conductive lead for transmission or electric field sensing and activating human muscles or organs. However, electricity is not completely safe for the human body; therefore, to avoid harming users careful consideration is essential when developing such devices. The knowledge required for such consideration is spread throughout a large number research fields, and it can be difficult for researchers in the HCI field to comprehend all of them. The purpose of this work is to support researchers in developing systems that apply electricity to the human body and to serve as a basis for further research. We review previous research pertaining to HCI in which users come into contact with electricity. In addition, considerations of how and where this type of research can be expanded, along with guidelines grounded in other fields for designing systems safely and addressing ethical concerns, are presented. An understanding of the field and of the related safety issues will enhance the understanding of limitations and potential and can clarify the design space.