Ayahuasca, also commonly called Yagé is a hallucinogenic brew that has been used by the indigenous people in the Amazon region for centuries. It contains a combination of substances and induces both physical and mental effects. The effects come on after about 15 to 60 minutes after ingestion and remain present between 2-6 hours.
The physical effects Ayahuasca triggers, depends on the composition of the brew and the ingested dose. Normally, the user will first be hit by a wave of nausea which can cause him to vomit, some will even encounter a mild case of diarrhea - the indigenous folks consider this a cleansing effect to reach a state of purity before one meets the spirits or gods of nature. In addition, any parasites, such as worms, are rinsed out of the body which frees the body from any distractions of the "old" reality and the body can absorb the active substances more readily. The nausea is not an inevitable evil, it has been observed that most cultures use a special diet to diminish the effect. Other caused physical effects could be a slight humming in the ear, tremors, cold flashes, intense sweating, swindle and a slight increase of the blood pressure and pace of heartbeat. There are no documented cases of a fatal overdose but allergic reactions to the substances can not be excluded. But as a rule of thumb, if you ingest an overdose of Ayahuasca, you will most likely simply black-out and ruin the experience, nothing else. Continuous use of Ayahuasca is not known to cause long term effects on the mental health of the user and it is not known to be addictive. The one great concern in using Ayahuasca is the raising levels of Tyramine which can cause a hypertensive crisis, ending in a hemorrhagic stroke and rapture of an existing aneurysm or and myocardial infraction, which in result can cause the death of the user. But this is just theoretical and has never been documented. Aside from the theoretical danger, there is a study that shows that Ayahuasca is a very good remedy for depression, addiction and anxiety disorders.
Ayahuasca contains powerful hallucinogenic alkaloids and induces the most profound of all psychedelic experiences. The use of different admixture plants modifies the effects, but the most affected sense during these psychedelic Ayahuasca experiences is vision. The experiences are described as dream-like sequences including the manifestation of spiritual (plant) helpers, demonic creatures, deities and all sorts of animals. Some see sequences of floating fractals and geometrical patterns and/or experience the amazing feeling of flying, while others believe they can see things at a great distance and events in the future. The user literally experiences a totally different world than the cold hard reality he is used to and reaches a state of divinity in which he can visit unimaginable places such as paradise or hell. It is also possible to experience your own death. All those effects make it pretty plain to see why the Mestizos used Ayahuasca to separate the soul from the physical body for their spiritual and religious purposes.