Hydroxyzine is a first-generation antihistamine of the diphenylmethane

Diphenylmethane

Diphenylmethane is an organic compound with the formula 2CH2. The compound consists of methane wherein two hydrogen atoms are replaced by two phenyl groups...

 and piperazine

Piperazine

Piperazine is an organic compound that consists of a six-membered ring containing two opposing nitrogen atoms. Piperazine exists as small alkaline deliquescent crystals with a saline taste....

 classes. It was first synthesized by Union Chimique Belge in 1956 and was marketed by Pfizer

Pfizer

Pfizer, Inc. is an American multinational pharmaceutical corporation. The company is based in New York City, New York with its research headquarters in Groton, Connecticut, United States...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 later the same year, and is still in widespread use today.

Hydroxyzine is used primarily as an antihistamine

Antihistamine

An H1 antagonist is a histamine antagonist of the H1 receptor that serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions...

 for the treatment of itch

Itch

Itch is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to classify it as any one type of sensory experience. Modern science has shown that itch has many similarities to pain, and while both are unpleasant sensory experiences, their behavioral response...

ing, allergies

Allergy

An Allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person's immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid...

, hyperalgesia

Hyperalgesia

Hyperalgesia is an increased sensitivity to pain, which may be caused by damage to nociceptors or peripheral nerves. Temporary increased sensitivity to pain also occurs as part of sickness behavior, the evolved response to infection.-Types:...

, motion sickness

Motion sickness

Motion sickness or kinetosis, also known as travel sickness, is a condition in which a disagreement exists between visually perceived movement and the vestibular system's sense of movement...

-induced nausea

Nausea

Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...

, and insomnia

Insomnia

Insomnia is most often defined by an individual's report of sleeping difficulties. While the term is sometimes used in sleep literature to describe a disorder demonstrated by polysomnographic evidence of disturbed sleep, insomnia is often defined as a positive response to either of two questions:...

, as well as notably for the treatment of mild anxiety

Anxiety

Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...

.