Lysergic acid diethylamide

Lysergic acid diethylamide (LSD) is a powerful hallucinogenic commonly known as acid. LSD stimulates centers of the sympathetic nervous system in the midbrain, which leads to pupillary dilation, increase in body temperature, and rise in the blood-sugar level. LSD also has a serotonin-blocking effect.

Although most LSD trips include both pleasant and unpleasant aspects, the drug's effects are unpredictable and may vary with the amount ingested and the user's personality, mood, expectations, and surroundings.

Users of LSD may experience some physiological effects, such as:
Increased blood pressure and heart rate
Dizziness
Loss of appetite
Dry mouth
Sweating
Nausea
Numbness
Tremors
However, the drug's major effects are emotional and sensory. The user's emotions may shift rapidly through a range from fear to euphoria, with transitions so rapid that the user may seem to experience several emotions simultaneously.