LSD is the most common hallucinogen and one of the most potent mood-changing chemicals. It is manufactured from lysergic acid, found in a fungus that grows on rye and other grains. LSD, commonly referred to as "acid," is sold on the street in tablets, capsules, and occasionally in liquid form. It is odorless and colorless, with a slightly bitter taste. Users refer to positive LSD experiences as a "trip," and to acute adverse reactions as a "bad trip." Users may experience panic, confusion, suspicions, anxiety, and loss of control. Flashbacks also occur after they stop taking the drug.