This reference provides an up-to-date compilation of background scientific information that advocates the application of currently developed clinical studies of the effects of aromatherapy to the treatment of human diseases such as mild, stress-induced mood disorders, infectious diseases, and age-related disturbances. It presents a rational basis for clinical translations of aromatherapy for treating human diseases in need of safer or more effective therapies and discusses the need for further clinical development in areas where therapy is lacking.