Also known as. The term ichthyoallyeinotoxism comes from the Greek words ichthus (fish), aluein (to be out of oneself, to hallucinate), and toxikon (venom). It is used to denote a rare hallucinogenic intoxication due to the consumption of the head or other body parts of a fish belonging to the group of * dream fish, many species of which are indigenous to the Indian and Pacific Oceans, and the Mediterranean Sea. Because of their psychoactive effects, such fish species are referred to as *psychoactive fauna. Ichthyoallyeinotoxism is classified as a variant of ichthyosarcotoxism, i.e.food poisoning caused by the ingestion of fish. The symptoms typically commence within a few minutes to 2 h after the consumption of fish, and they usually last no longer than 36 h. Ichthyoallyeinotoxism is characterized by generalized malaise and a variety of CNS disturbances such as nausea, vertigo, disturbances in motor coordination, vivid *visual and/or *auditory hallucinations, * nightmares, and sometimes frank * delirium. The hallucinations occurring in the context of ichthyoallyeinotoxism are sometimes compared to those occurring in LSD intoxication. The toxin or toxins responsible for the mediation of ichthyoallyeinotoxism are unknown. As all ichthyoallyeinotoxic fishes appear to be algal grazers, it is believed that they may derive their hallucinogenic properties from alkaloids of the indole group, which are chemically quite similar to LSD, and which occur naturally in certain types of algae and phytoplankton. It has also been suggested that ichthyoallyeinotoxism may be mediated by * dimethyltryptamine (DMT), a * hallucinogen even more potent than the indoles present in fish.