Smart textiles, also referred to as e-textiles or intelligent fabrics, represent a rapidly evolving interdisciplinary field that integrates advanced materials, electronics, and information technology into traditional fabrics to enable real-time health monitoring. These textiles are embedded with sensors, conductive fibers, and microelectronic components capable of detecting physiological parameters such as heart rate, respiratory rate, body temperature, muscle activity, blood oxygen saturation, and even biochemical markers in sweat. The integration of wireless communication modules allows continuous data transmission to smartphones, wearable devices, or cloud-based platforms for analysis, enabling early detection of health anomalies and facilitating remote patient monitoring. Advances in nanotechnology, flexible electronics, and energy harvesting have significantly improved the comfort, durability, and washability of smart textiles, making them suitable for everyday use in healthcare, sports, and rehabilitation settings. Moreover, artificial intelligence (AI) algorithms are increasingly being applied to the collected data to provide predictive analytics and personalized health recommendations. Despite their potential, challenges remain in terms of sensor calibration, long-term biocompatibility, power management, data privacy, and manufacturing scalability. Future developments are expected to focus on fully self-powered textiles, biodegradable sensors, and seamless integration with telemedicine platforms, creating a new paradigm in preventive and personalized healthcare. This paper explores the materials, design approaches, sensing technologies, data analytics integration, and emerging applications of smart textiles for health monitoring, as well as the challenges and opportunities that will shape the next generation of intelligent wearable health systems.