D-allose has attracted a great deal of attention in recent years due to its many pharmaceutical activities, which include anti-cancer, anti-tumor, anti-inflammatory, anti-oxidative, anti-hypertensive, cryoprotective, and immunosuppressant activities. D-allose has been produced from D-psicose using D-allose-producing enzymes, including L-rhamnose isomerase, ribose-5-phosphate isomerase, and galactose-6-phosphate isomerase. In this article, the properties, applications, and metabolism of D-allose are described, and the biochemical properties of D-allose-producing enzymes and their D-allose production are reviewed and compared. Moreover, several methods for effective D-allose production are suggested herein.