Wet Dreams, Tapeworms, and Fetal Sex Change: Ritual and Medicinal Uses of Realgar in Premodern Japan

Realgar (Ch. xionghuang; Jp. yūō 雄黄), an arsenic sulphide mineral, is a well-known ingredient of Chinese traditional medicine, and is also widely mentioned in Buddhist and alchemical literature. Among its many qualities, realgar is said to be efficacious against poisons and poisonous animals, specifically snakes, to cure ulcers and skin diseases, and it has also been utilised to protect from demonic attacks. However, comparatively less is known about the role of this mineral in the Japanese context.

This paper proposes to investigate the ritual uses and medical applications of realgar in premodern Japan by focusing on a selection of personal diaries written by courtiers of the Heian period (794 - 1185), coeval medical treatises, and Buddhist ritual manuals. What emerges from these sources is that realgar was indeed believed to dispel demons and quell agitated states of mind. However, it seems to have been more widely employed as one of the remedies to treat tape-worms infestations.

Aside from looking at the ways in which Japanese physicians and Buddhist monastics made sense of this material vis-à-vis sources and practices coming from the mainland, this paper will also interrogate the interpretations and practical uses unique to this context.