As more Westerners travel to the Amazon jungle to seek healing through the increasingly popular plant medicine, ayahuasca, they are exposed to an environment pervaded by the use of tobacco smoke. Mapacho is the name of the potent jungle tobacco that is central to the shamanic practices of Amazonian plant medicine healing, regarded locally not as a pathogen but rather as a potent ally: a spirit that can be co-opted as a purifier, healer, protector and teacher. In order to render these functions available to patients, Mapacho must be smoked, its efficacy, along with that of the shaman, activated through the absorption of each into the other. By means of this relationship, Mapacho smoke pervades culturally recognised boundaries of the Western Self, simultaneously permeating both the internal and external realms that constitute the healing environment. In this paper, I explore the relationship between Mapacho, Peruvian Shipibo shamans and Western patients, suggesting that the boundaries that are often conceived by Westerners to distinguish each from the other may well be as smoky as the medicine practices they engage in.