Hallucinogens, or psychedelics, are a group of drugs that alter a person’s perception of reality. They also change a person’s thoughts and feelings. Types of hallucinogens include LSD, peyote, PCP, psilocybin and others. Nearly all hallucinogens are illegal, and researchers don’t consider any amount of use safe.


Hallucinogens can cause many unpleasant side effects, including increased body temperature, excessive sweating and tremors.
Hallucinogens can cause many unpleasant side effects.

What are hallucinogens?

Hallucinogens are a type of drug that changes a person’s awareness of their surroundings. Also known as psychedelics, they alter a person’s thoughts and feelings, as well. Some hallucinogens are human-made (synthetic), and some come from naturally occurring compounds found in certain plants and fungi (plural of fungus).

Hallucinogenic drugs can cause hallucinations, which are sensations and images that seem real but aren’t. People may hear, feel or see things that aren’t really there. Some psychedelic drugs cause people to feel out of control or disconnected from their bodies and environment.

The effects of the different drugs vary, but they all affect your senses, thoughts and mood. If a person is under the influence of a hallucinogen, they’re said to be “tripping.” People can have “good trips,” where the experience is positive, or “bad trips,” where the experience is negative.

People have used hallucinogens for religious and healing rituals for centuries. More recently, people use the drugs for recreational purposes. Healthcare providers don’t consider any amount of psychedelic drug use safe. However, scientists are now looking into the possibility of using certain hallucinogens as provider-supervised treatments for mental health conditions, including depression and anxiety.


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How do hallucinogens work?

Hallucinogens work by disrupting communication between chemical networks throughout a person’s brain. For instance, some work by interfering with a chemical (neurotransmitter) called serotonin. Serotonin controls various functions in a person’s body, including:

  • Sleep.
  • Hunger.
  • Mood.
  • Body temperature.
  • Sensory perception.

Other hallucinogenic drugs interfere with the neurotransmitter glutamate, which regulates:

  • Emotions.
  • Pain perception.
  • Learning and memory.
  • Responses to the environment.

What is LSD?

The meaning of LSD is lysergic acid diethylamide. Made from lysergic acid, this drug is one of the strongest mind-altering chemicals. A fungus that grows on rye and other grains contains this chemical. LSD, or acid, looks like a clear or white material. People usually soak small squares of blotting paper in the LSD. Then, they swallow these acid tabs. LSD can also come as a tablet or capsule.

The effects of LSD make a person lose touch with reality. They may have mystical experiences, such as visions or blending of their senses. For instance, they may smell sounds or hear colors. The effects of LSD can last for nine to 12 hours.

LSD isn’t considered addictive because it doesn’t cause uncontrollable drug-seeking behavior. But repeated use can build up a person’s tolerance, so they have to take a higher dose to achieve the same effect.

What is peyote?

Peyote is a small, spineless cactus in which the main active ingredient is mescaline. Mescaline is a naturally occurring substance found in the peyote cactus. The top of the peyote cactus, also referred to as the crown, consists of disk-shaped buttons that people cut from the roots and dry. People generally chew the buttons or soak them in water to produce an intoxicating liquid.

The hallucinogenic dose of mescaline is about 0.3 to 0.5 grams, and its effects last about 12 hours. Because the extract is so bitter, some people prefer to prepare tea by boiling the cacti for several hours. Peyote can also be human-made (synthetic).

Peyote is one of the oldest known psychedelics. Native Americans used it prominently as part of their culture. Peyote has different emotional and mental effects depending on a person’s body type, personality, drug history and expectations. Some common effects may include:

  • Vivid mental images.
  • Altered perception of space and time.
  • Distorted sense of body.
  • Loss of sense of reality.

What is psilocybin?

Psilocybin comes from certain types of mushrooms found in tropical and subtropical regions of the United States, Mexico and South America. Other names for the hallucinogen include magic mushrooms or ’shrooms. These mushrooms usually contain less than 0.5% psilocybin plus trace amounts of psilocin, another hallucinogenic substance.

You can cook the psilocybin mushroom, boil it into a drink or eat it raw. To mask the bitter flavor of the mushrooms, psilocybin chocolate has become popular. People have developed recipes using mushrooms and chocolate together to get the same effect with a less bitter taste.

Psilocybin can cause a wide range of effects from heightened sensory awareness to impaired judgment. “Bad trips” may cause frightening hallucinations, terror, depression or panic attacks.

What is PCP?

PCP stands for phenylcyclohexyl piperidine, but you may also see the term phencyclidine. Other names for PCP include angel dust and killer weed. It comes in a variety of forms, including liquids, powders, tablets and capsules. People usually swallow, sniff or inject the drug, but they can also smoke it.

Scientists developed the PCP drug in the 1950s for use as a general anesthetic. But providers stopped using it for this purpose in 1965 due to serious side effects.

PCP creates an out-of-body feeling. Coming down from it causes a numbing effect that can cause a person to become agitated and irrational. When used at high doses, PCP can cause seizures, coma and death. Deaths typically occur when a person dies by suicide or has a fatal accident due to their altered state.

What is ketamine?

Ketamine is an anesthetic that healthcare providers use for surgery on humans and animals. Much of the ketamine people use is stolen from veterinary offices. People usually snort it as a powder or swallow it as a pill, but they can also inject it as a liquid.

The effects of ketamine include an out-of-body feeling. For some people, this may be a pleasant sensation but for others, it can be terrifying.

What is salvia?

Salvia divinorum, more commonly referred to as salvia, is a plant found in southern Mexico and Central and South America. People usually ingest salvia by chewing its leaves or by drinking juices extracted from the plant. They also smoke or vaporize and inhale the dried leaves of the salvia plant. Other names include sage of the seers and the diviner’s sage.

The effects of salvia include visions and hallucinations, such as the blending of senses. It can also make people feel like they’re floating above the ground or traveling through time.

What is DMT?

DMT stands for dimethyltryptamine. Some plants in the Amazon contain this naturally grown chemical. Ayahuasca is a type of tea made from these plants. As a tea, DMT is known as hoasca, aya or yagé.

DMT can also be human-made (synthetic). People make it in a lab. In this form, it’s usually a white powder that you smoke.

What adverse effects do hallucinogens have on health?

Unpleasant adverse effects due to the use of hallucinogens are common. These result from the large number of psychoactive ingredients in the hallucinogen. The effects depend largely on the amount taken. Adverse effects may include:

Specifically, PCP use is associated with a wide range of adverse effects. At low-to-moderate doses, a person may experience a slight increase in their breathing rate and a pronounced rise in their blood pressure and pulse rate. In addition, they may experience:

  • Shallow breathing (tachypnea).
  • Flushing and excessive sweating.
  • Generalized numbness of their extremities.
  • Loss of muscular coordination.

At high doses, PCP use can lead to adverse effects including:

PCP use often leads to emergency room visits due to overdose or because of the drug’s severe psychological effects. While intoxicated, PCP users may become violent or suicidal and are therefore dangerous to themselves and others.

High doses of PCP can also cause seizures, coma and death. Death more often results from accidental injury or suicide during PCP intoxication. Because PCP can also have sedative effects, interactions with other central nervous system depressants, such as alcohol, can lead to coma.


What treatment options exist?

People sometimes seek treatment for hallucinogen intoxication as a result of “bad trips,” during which a person may, for example, hurt themselves.

Treatment is usually supportive. A provider will place the person in a quiet room with little sensory stimulation. Occasionally, the provider will recommend a medication such as benzodiazepine (Xanax®) to manage extreme agitation or seizures.

There are no specific treatments for drug use and substance use disorder (SUD). But inpatient and/or behavioral treatments may be helpful for people with a variety of substance use disorders.

Additional Common Questions

Is weed a hallucinogen?

Yes, researchers classify weed (cannabis) as a hallucinogen. Although marijuana doesn’t always produce hallucinogenic effects, it can do so at high doses.


Can hallucinogens be used as medicines?

Psychedelic research has slowly been making its way back into modern science. Many clinical studies have shown the potential of psilocybin as a promising treatment option for certain mental health conditions, including depression, anxiety and other mood disorders. In addition, researchers have demonstrated that psilocybin may also have an effect as a treatment option for:

A note from Cleveland Clinic

Nearly all hallucinogens are illegal, and researchers don’t consider any amount of drug use safe. The drugs can cause many adverse effects to your health and well-being. The use of these hallucinogens can cause serious harm to you and the people around you. Long-term continued use can lead to dependence. If you have questions about the use of hallucinogens or you think you may be experiencing substance use disorder, reach out to your healthcare provider for help. You don’t have to go it alone.

Medically Reviewed

Last reviewed on 04/18/2023.

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