Ayahuasca is a traditional Inca hallucigenic plant. Intoxication by Ayahuasca is an introspective dysleptic experience with a high emotional tonality, particularly well memorised. It can be complicated by physical discomfort, terror reactions, and fits of delirium. The leaves of Ayahuasca contain dimethyltryptamine (DMT), and the creepers contain beta-carboline alkaloids (THH). DMT is a serotoninergic agonist, close to LSD. The beta-carbolins inhihibit type A monoamine-oxydases that break down DMT in the intestine and allow passage through the intestinal wall and prolong its actions. The beta-carbolins give Ayahuasca its purgative and emetic effects. There have been a number of debates on the use of Ayahuasca as a therapy. The promoters suggest its use for the treatment of certain addictive pathologies. It will allow a highly emotionally charged access to the unconscious in spiritualistic contexts with groups that have a chamanistic resonance. This approach is challenged by scientific spheres which point out the methodological weakness of these studies and the absence of detachment regarding the subjects’ relapses and suggestibility. The authors bring to the fore the risks of distortions of affective perception, the over-investment of personal experience and the primacy of subjectivism, and the weakening of the system of reality. This gives rise to ways of thinking that are paralogical, interpretative, intuitive and highly inspired by passion. This, in turn, attracts the most vulnerable and suggestible subjects, entrains a rigidness of psychic processes and an impoverishment and a narrowing of emotional life around the object that is Ayahuasca. Health authorities have classified Ayahuasca as a dangerous substance on the same grounds as other psychodysleptics.