Ayurveda is ascribed a divine origin. Many different sources tell about different gods and people about the origin of Ayurveda. In Kerala Ayurveda practicing starts with addressing Dhanwantary Gods (Rudra Dhanwantarikal) in plural, not as a single entity. They also ascribe the origin of Ayurveda to Aswini Gods.
There is confusion about Dhanwantary as an incarnation of Lord Vishnu or a group of gods who transcribed the knowledge of life (Ayurveda) to humankind.
A story tells Lord Dhanvantary appeared from the ocean with a pot of divine nectar of immortality, while the gods and demons were churning the ocean of milk (palazhi). This story undermines Dhanvantary as an incarnation of Lord Vishu, because Lord Vishnu was in the form of a tortoise supporting the Mandara Mountain, which was used to churn the ocean.
This dhanvantary has four arms, each bearing different items signifying the different specialties in Ayurveda. One among the objects is a leech, signifying surgery in Ayurveda.
A re-incarnation of this Dhanvantary occurred when the King of Kasi was able to ask Lord Dhanvantary as his son. Lord Dhanvantary, responding to the deep penance the King of Kasi was in, agreed to be born in human form. He, as the son of the King of Kasi remained an ascetic, but was forced to become the King of Kasi. He prepared the treatises of Ayurveda on all the eight limbs of Ayurveda.
The story of Ashwini Gods
Ashwini Gods or Aswini kumaras were said to present the knowledge of Ayurveda to Lord Indra, the king of Gods. Lord Indra gave this knowledge to Dhanvantari, Kashayapa and Bharadwaj. These three seers are still held in esteemed position by Ayurveda practitioners.
Aswini Twins and Lord Dhanvantary (Dhanvatars) are regarded as gods of Ayurveda.