What Does Hydroxyzine Do? A Complete Guide to This Antihistamine

October 7, 2025 •

3 min read

First-generation antihistamines, including hydroxyzine, have been prescribed for decades due to their ability to cross the blood-brain barrier and exert effects on the central nervous system. However, understanding what does hydroxyzine do, beyond its allergy relief, is crucial for patients, as it has multiple applications from managing anxiety to aiding in sedation.

Quick Summary

Hydroxyzine is a prescription antihistamine primarily used for short-term anxiety, itching caused by allergies, and sedation before surgery. Its sedative effects, caused by blocking histamine in the brain, provide calming relief, but it is not intended for chronic use due to potential cognitive risks.

Key Points

Dual Action Medication: Hydroxyzine acts as both an antihistamine to relieve allergic itching and a central nervous system depressant to reduce anxiety and induce sedation.
Fast-Acting Relief: Many people experience a calming effect within 15 to 30 minutes, making it suitable for acute or situational anxiety and immediate allergy relief.
Short-Term Use Recommended: Due to potential side effects like drowsiness and cognitive issues, especially in older adults, hydroxyzine is generally prescribed for short-term use, typically under four months.
Non-Addictive Alternative: Unlike benzodiazepines such as Xanax, hydroxyzine is not a controlled substance and does not carry the same risk of dependency or withdrawal.
Common Side Effects: The most frequent side effects include drowsiness, dizziness, dry mouth, and headache.
Important Safety Precautions: Patients should avoid alcohol and other depressants, and those with certain heart conditions or the elderly require careful medical supervision.

Hydroxyzine: A Versatile Antihistamine

Hydroxyzine, known by brand names like Atarax and Vistaril, is a first-generation antihistamine with applications beyond typical allergy treatment. Introduced in 1956, it's used for short-term anxiety relief, managing allergic itching, and inducing relaxation before medical procedures. Its effectiveness comes from its impact on both histamine and other neurochemicals.

How Hydroxyzine Works in the Body

Hydroxyzine primarily works by blocking histamine H1 receptors in both the brain and the body. This action explains its various uses and side effects.

Blocking Histamine for Allergic Relief

During an allergic reaction, histamine is released, causing symptoms like itching and hives. By blocking H1 receptors, hydroxyzine prevents histamine from acting, thus alleviating allergic skin conditions such as chronic urticaria and atopic dermatitis. Relief from itching typically occurs within 15 to 30 minutes after taking it orally.

Affecting the Central Nervous System for Anxiety and Sedation

Unlike newer antihistamines, hydroxyzine easily enters the brain, where it blocks H1 receptors and influences other systems, including serotonin. This effect on the central nervous system (CNS) provides its calming, sedative, and anxiety-reducing properties. It can help to:

Relieve anxiety and tension: It can reduce restlessness and worry in the short-term management of generalized anxiety disorder and situational anxiety.
Induce sedation: Its sedative effect is beneficial for relaxing patients before and after procedures.
Aid with insomnia: The drowsiness can help with sleep difficulties linked to anxiety.

Primary Medical Uses for Hydroxyzine

Allergies and Pruritus: Effective for histamine-related itching from conditions like chronic hives and allergic skin reactions.

Anxiety: Approved by the FDA for short-term management of generalized anxiety disorder symptoms like nervousness.

Sedation: Used to promote relaxation and drowsiness, particularly before medical procedures.

Off-Label Uses: May be used for nausea, vomiting, and alcohol withdrawal symptoms due to its antiemetic properties.

Hydroxyzine vs. Benzodiazepines for Anxiety

Comparing hydroxyzine and benzodiazepines like Xanax reveals significant differences in their use for anxiety.


Feature	Hydroxyzine	Benzodiazepines (e.g., Xanax)
Drug Class	Antihistamine	Benzodiazepine
Primary Mechanism	Blocks histamine H1 and affects serotonin, calming the CNS.	Enhances GABA, which calms the nervous system.
Onset of Action	Fast, usually 15-30 minutes.	Very fast, within 15-30 minutes.
Addiction Potential	Not addictive; not a controlled substance.	High potential for addiction and dependence; controlled substances.
Long-Term Use	Not recommended for long-term (over 4 months) use due to potential cognitive side effects.	Limited to short-term use due to high risk of dependency.
Withdrawal	Lower risk of withdrawal.	Can cause severe withdrawal symptoms.
Primary Use	Mild-to-moderate anxiety, allergies, sedation.	Severe anxiety, panic attacks.

Important Side Effects and Precautions

Common side effects of hydroxyzine are often related to its sedative effects.

Common Side Effects:

Drowsiness, fatigue, dizziness.
Dry mouth, headache, constipation.
Blurred vision.

Less Common or Serious Side Effects:

Heart Rhythm Issues: Can cause QT interval prolongation, a rare heart problem, especially with other interacting medications.
Confusion: Higher risk for older adults, who should generally avoid this medication.
Increased Fall Risk: Sedation increases the risk of falls, particularly in the elderly.
Urinary Retention: Difficulty urinating is a serious potential anticholinergic effect.
Severe Skin Reactions: Rarely, a severe rash called AGEP can occur.

Precautions and Contraindications:

Interactions: Avoid alcohol and other CNS depressants to prevent amplified sedative effects. It can also interact with medications causing drowsiness or affecting heart rhythm.
Pregnancy: Should be avoided, especially in the first trimester.
Elderly Patients: Use cautiously due to increased risk of cognitive side effects, sedation, and falls.

Conclusion

Hydroxyzine is a rapid-acting antihistamine with multiple uses for allergic itching and short-term anxiety. Its unique mechanism of blocking histamine and affecting neurotransmitters provides a non-addictive option for anxiety relief. However, due to sedative and anticholinergic effects, it's best for short-term, as-needed use, with alternatives like SSRIs often preferred for chronic anxiety. Always consult a healthcare provider to discuss the risks and benefits and determine the best treatment plan.

For more detailed information, consult the MedlinePlus drug information page on hydroxyzine: https://medlineplus.gov/druginfo/meds/a682866.html.

Frequently Asked Questions

Hydroxyzine is a versatile medication that is approved to treat both allergies and anxiety. It functions as an antihistamine to combat allergic itching, but its effect on the central nervous system also makes it effective for providing short-term relief from anxiety and inducing sedation.

For most people, the calming effects of hydroxyzine begin relatively quickly, often within 15 to 30 minutes of taking an oral dose. Full effects may be felt within two hours, and the effects generally last for four to six hours.

No, hydroxyzine is not considered addictive or habit-forming and is not a controlled substance. This is a key difference from benzodiazepines like Xanax, which have a high potential for dependence and require careful tapering to avoid withdrawal symptoms.

No, hydroxyzine is not recommended for long-term treatment of anxiety, typically not for more than four months. Long-term use can lead to tolerance and has been associated with potential cognitive side effects, especially in older adults, due to its anticholinergic properties.

The most common side effects of hydroxyzine include drowsiness, dizziness, dry mouth, headache, and fatigue. Taking the medication at bedtime, if appropriate, can help manage daytime drowsiness.

Hydroxyzine is often not recommended for elderly patients (65 and older) due to an increased risk of side effects such as confusion, excessive sedation, falls, and urinary retention. Safer alternatives are often preferred for this population.

No, you should avoid drinking alcohol while taking hydroxyzine. Alcohol can increase the sedative effects of the medication, leading to excessive drowsiness, dizziness, and impaired coordination.