Uses: Dried Cassia bark is the spice. The essential oil is called cassia cinnamon oil (Oleum Cinnamon). Apart from its use as a spice, it is a well-known medicine reinforcing ‘yang’, the body fire. ‘Gui Zhi’ (dried twig of cassia cinnamon) is collected in spring and summer and dried in the sun or in the shade used in decoctions, has analgesic and antipyretic properties.