LSD is a type of psychedelic drug that can lead to hallucinations. It's also called acid. LSD alters a person's ability to think and feel. It can cause changes in sensation and emotions.

In its pure state, LSD is a white, odorless powder. It's often sold in liquid form or as tablets or capsules. It's often put on absorbent paper. This paper is then cut into small, decorated squares. Each square is one dose.

LSD is very powerful. Small amounts can cause strong effects. These effects are hard to predict. They often start 30 to 90 minutes after taking the drug. They are strongest 3 to 5 hours later. They can last for up to 12 hours.

The typical effects of LSD include:

• Intense sensory experiences (brighter colors and sharper sounds).
• Mixing of the senses (colors are heard or sounds are seen).
• Distorted sense of time and space (minutes can seem as long as hours).
• Distorted body image (a person feels as if they are floating or being pulled down by gravity).

The physical effects of LSD include:

• Dilated (enlarged) pupils.
• Raised body temperature.
• Increased heart rate and blood pressure.
• Sweating.
• Loss of appetite.
• Sleeplessness.
• Dry mouth.
• Shaking (tremors).

While using LSD, or “tripping,” a person may feel anxiety or fear. The hallucinatory effects can be unpleasant, such as spiders crawling on the skin. Or they can be so strong the person feels like they are losing control.

Having a bad reaction to LSD and similar drugs is common. The scary sensations may last a few minutes or several hours. They can be mildly frightening or terrifying. The person may feel panicked, confused, suspicious, anxious, and helpless.

Often the bad feelings go away when the drug wears off. But some people have them for several days after. Sometimes these effects can last weeks or months.

Some people can have a flashback. They may have a repeat experience of the effects days, weeks, or even years after using the drug. The person may see intense colors and other hallucinations. The flashback can seem pleasant. Or it may produce severe anxiety.

Flashbacks most often occur in people who used LSD over a long period. They also tend to occur in people who have a history of a mental health condition. But they can happen to anyone. People who use a lot of LSD may develop long-term (permanent) brain damage, such as problems with memory and attention span.

LSD's effects vary from person to person. They depend on many factors. These include the person's size, weight, and health. It also matters how much of the drug is taken, the quality of the drug, and if it's used with other drugs.

It's not safe to drive after using LSD. Sensory and perceptual distortions may cause the person to see things that affect driving.

If someone has a bad reaction to LSD, seek medical help right away. Stay with the person until they get care.