Hallucinogens are natural and synthetic substances that when ingested, significantly alter one's state of consciousness. Hallucinogenic compounds often cause people to envision or perceive random colors, patterns, events, and objects that do not exist. Many different types of substances are classified as hallucinogens, solely because of their capacity to produce such hallucinations.

Some users of hallucinogens have reported feeling mystical and insightful, while others are fearful, paranoid, and hysterical. Unlike such drugs as barbiturates and amphetamines, hallucinogens are not physically addictive; however, people can become psychologically dependent upon them. The real danger of hallucinogens is not their toxicity, but their unpredictability. People have had extremely varied reactions to these substances, especially to LSD (lysergic acid diethylamide), that it is virtually impossible to predict the effect a hallucinogen will have on any given individual.

When produced naturally, hallucinogens are formed in dozens of psychoactive plants, including the peyote cactus...