Exploring On-Skin Interfaces as Interactive Intelligent Technologies for Health Diagnostics: Systematic Review of Current Practices and Future Directions

On-skin interfaces are emerging as intelligent, non-invasive technologies that enable continuous physiological monitoring and health diagnostics. This systematic review explores the current landscape, design practices, effectiveness, and ethical implications of on-skin interfaces in healthcare. A total of 174 peer-reviewed studies published between 2015 and 2025 were identified across six major databases and analyzed to synthesize trends in sensor application, body placement, user interaction, and diagnostic focus. Findings reveal that most systems are concentrated on physical health (e.g., cardiac, respiratory, hydration), with limited but growing attention to mental and behavioral health contexts. Despite promising technical performance, the widespread clinical adoption of these technologies is hindered by challenges in real-world validation, signal robustness, long-term wearability, and a lack of personalized feedback, and only 21 studies (12.1%) evaluated the technology from the perspective of its users. Five core design recommendations emerged: enhancing clinical feasibility, ensuring user comfort, improving signal generalizability, incorporating intervention-driven interfaces, and embedding ethical safeguards. This review highlights a growing need for user-centered and ethically responsible design strategies that extend beyond monitoring to actionable interventions. The findings offer a roadmap for advancing on-skin interfaces into intelligent, interactive health companions capable of supporting both short- and long-term care. Bridging research innovations with clinical application will be essential to realizing the full potential of these technologies in personalized and preventive healthcare.