Hallucinogen

A hallucinogen is a pharmacological substance that when ingested causes hallucinations - profound distortions in a person's perceptions of reality. Under the influence of hallucinogens, people see images, hear sounds, and feel sensations that seem real but do not exist. Some hallucinogens also produce rapid, intense emotional swings. Hallucinogens cause their effects by disrupting the interaction of nerve cells and the neurotransmitter serotonin. <ref>http://www.drugabuse.gov/ResearchReports/hallucinogens/halluc2.html<?ref> Hallucinogenic substances may be synthetically manufactured in a laboratory like LSD or derive from natural plant (e.g peyote, cannabis), fungi (e.g magic mushrooms) or animal (Colorado River toad) sources.

Natural sources have long been used in shamanic cultures as a way of communicating with the spirits or gods, or as a means of divination and prophesy.

Only a few hallucinogens actually produce hallucinations where things that are not real, appear to be realistic.