It is no longer purge but vision.
The ayahuasca brew is known locally as "the purge": rather than to address a specific disease, the locals consume it to cleanse the stomach and the blood, throw up bad energy and attract good luck: hunting, sales, wife or husband. Thus, the purgative property of the remedy (result of the vine´s alkaloids, Banisteriopsis caapi) is privileged for its visionary property (due to the DMT of the chacruna, Psychotria viridis, or the huambisa, Dyplopteris cabrerana).
Westerners, in popular texts and widespread opinion, celebrate DMT; the vine´s function is to allow the DMT not to be destroyed in the stomach but instead reach the bloodstream. They show tolerance with the natives, because they gave the drink the name of the less important plant in the formula. Vision happens to be an obsession in the West: they only care about the DMT and the supposed fantastic worlds it delivers. Assumptions: colourful visions are rarely reached, visions that are that well reproduced by artist Debernardi Anderson in his paintings.