Terahertz radiation situated between infrared and milimeter waves on the electromagnetic spectrum has concentrated considerable attention on its remarkable potential in medical diagnosis and biomedical applications over the last three decades. The exploration of terahertz interaction with biological systems has given rise to an exciting field in the life sciences. Terahertz radiation demonstrated its ability to diagnose various diseases like brain cancer, thyroid nodules, and eye conditions. This comprehensive review delves into the biological attributes of THz waves and their clinical applications, with a primary focus on the remarkable progress made in utilising THz technology for head and neck diseases. We examine the current state of research, offering insights into the promising role of THz technology in enhancing diagnosis and treatment for these specific conditions.