Common hallucinogens used are LSD, psilocybin, mescaline, PCP, and morning glory seed. Hallucinogens are typically swallowed but sometimes can be inhaled. These drugs produce an altered state of consciousness and causes hallucinations both visual and auditory. Senses will become heightened and there will be a rise in heart rate and blood pressure. With the exception of PCP overdose does not happen but bad trips do. If a person is having an undesirable effect it is important to provide a calm environment and that person will eventually come out of it. PCP overdose includes psychosis, agitation, and really bad aggression. 
Psychedelics and hallucinogens are drugs that cause visual distortions. There are many forms of hallucinogens some are naturally found and some are manmade in lab by a chemist. Hallucinogens have been around for a very long time and some of the more natural forms of hallucinogens are used for spiritual and religious purposes. Hallucinogens can be abused but are not physically addictive in nature.
Mescaline is a hallucinogen that is found in peyote which is found in cactus and still commonly used in religious ceremonies. This hallucinogen produces psychedelic effects but can also have some negative effects such as nausea and vomiting. Mushrooms contain an ingredient called psilocybin which is another more common psychedelic and the street name for these mushrooms are magic mushrooms. LSD is a psychedelic drug that causes visual distortions. The street name for this drug is acid.
More Hallucinogens – PCP/Ketamine
PCP is a very dangerous drug. PCP affects 6 different transmitters at one time which are why this drug has an extremely intense effect. Some symptoms of PCP include delusions, violence, and suicidal thoughts. PCP is typically smoked. PCP is very unpredictable and causes people to act psychotic.
Ketamine is a dissociative that is generally used in animals for medical procedures. The street name for Ketamine is Special K and always starts as a liquid form. Once dried it can be smoked or snorted. Ketamine is found in veterinarian clinics but is sold on the street. Ketamine is a dissociative and can cause out of body experiences. Users often call this a K-hole. When in a K-hole time moves very slowly and the person is unable to talk or communicate.