A substance is qualified as "hallucinogenic" when it causes hallucinations. These agents are classified in the psychotropic category, and cause what is called an altered state of consciousness, including symptoms such as hearing voices and seeing things that do not exist. This state can affect all five senses. A hallucinogen can be a plant, a drug
like LSD, or other. These substances have an effect on the central nervous system, that can be severely impacted (to the point of causing death) in cases of overdose
. Contrary to so-called "delirogenic" substances, these agents do not cause mental confusion or memory lapses.