The story of origin of poison or visha in Hinduism is found in the Charaka Samhitha – is a Sanskrit text on Ayurveda. When the devas and the asuras were involved in the churning of the milky ocean, before the amruta or ambrosia emerged, a visha purusha, who was gigantic and terrifying, emerged.
Seeing the Visha Purusha, both the devas and asuras were grief-stricken and pleaded to the creator Brahma Dev to find a solution.
Brahma ordered Visha Purusha to abandon his terrifying form and to take refuge in creatures, plants and stones. Thus Visha Purusha entered various reptiles such as snakes, scorpions, spiders and so on.