Living systems emit what is called ultraweak photon emission (UPE). This visually undetectable phenomenon has only been studied in humans for the last 30 years, finding that UPE is a complex process depending on multitude factors. Considering previous literature, this review discusses the current trends in the analysis of in vivo UPE from human beings. To this aim, Analytical Approaches Employed for UPE Measurement section focuses on the analytical techniques employed (photomultipliers and charged coupled device cameras), summarizing analytical conditions and reporting figures of merit reached to date. Then, Human UPE Depending on External Factors and Human UPE Depending on Internal Factors sections address external and internal factors, which have proved to affect UPE, pointing out the important influence on oxidative processes outside and inside the body, and also highlighting some personal states of the individuals affecting UPE. Last section is devoted to give a general view on the goals and achieved up to date regarding UPE measurement, emphasizing some potential applications as well as recommendations which include: use of UPE spectra information together with UPE intensity, larger populations (≈50-100 subjects), further studies on internal states of individuals, and use of statistical tools.