How Long Does Hydroxyzine Stay in Your System?

With the potential side effects of medications, it’s common to wonder how long after you stop taking something it will continue to affect your body. This is an especially common concern for hydroxyzine since drowsiness is one of its side effects, and driving may be unsafe until it is out of your system.

This begs the question, how long does hydroxyzine stay in your system, and what might cause it to linger for longer? Continue reading to learn more.

Table of Contents

What Is Hydroxyzine?

Hydroxyzine belongs to the medication class of antihistamines, which block the action of histamine in the body. Histamine is responsible for allergic symptoms, making hydroxyzine a way to find relief from itching due to allergic skin reactions.

Beyond its applications for those with allergies, hydroxyzine may also be used alone or alongside other medications to relieve tension and anxiety in both children and adults. It can also be used with other medications as a sedative before and after surgery in children and adults. These applications are possible because of hydroxyzine’s ability to reduce activity in the central nervous system.

Even though anxiety is not an allergic reaction, it can be driven by histamine receptors that are a part of the central nervous system. Since hydroxyzine is able to block histamine, it can then be an effective treatment for anxiety. 

How Long Does Hydroxyzine Stay in Your System?

The half-life of hydroxyzine is around 20 hours, meaning it takes almost a day for half of the drug to leave your system. Estimates show that a drug remains in your system for around 5 half-lives, meaning hydroxyzine will stay in your system for an average of 100 hours, although its effects often wear off before this time.

How Does Hydroxyzine Compare to Similar Drugs?

When looking at how long hydroxyzine remains in your system, it can be helpful to look at similar drugs to see how it compares. In most cases, hydroxyzine remains in your system for much longer.

For example, another type of antihistamine is diphenhydramine, which is similarly used to treat allergic reactions. However, hydroxyzine lasts much longer in the body, with diphenhydramine having a half-life of only 3-9 hours, meaning it stays in the body for an average of only 30 hours compared to hydroxyzine’s 100.

Another antihistamine option is loratadine, which has a half-life of 8 hours and remains in the body for 40 hours.

As for similar anxiety medications, alprazolam is a common alternative. It has a half-life of 11 hours and a total time in the body of 55 hours after the last dose, putting it at around half the length of hydroxyzine.

However, alprazolam is a controlled substance that can be habit-forming and addictive, so hydroxyzine is often preferred for anxiety treatment. Still, this will depend on if the patient has any health conditions that make them incompatible with hydroxyzine.

What Can Affect How Long Hydroxyzine Stays in Your System?

While hydroxyzine is estimated to remain in the body for 100 hours, this is only an estimate based on an average of all those who take hydroxyzine. As such, some people may have the drug leave their body sooner than 100 hours, while others find that the drug lingers for longer than 100 hours.

The following are some of the key factors that can influence how long it stays in your system:


Hydroxyzine is effective in both children and adults, but the amount of time it stays in these two age groups’ systems can vary.

The standard half-life of hydroxyzine is 20 hours, but it can be shorter in children and longer in older adults. This means that children will not have it in their system for as long, while seniors will have to be careful with other medications they take or other variables that cause drug interactions for a longer amount of time.

Liver and Kidney Function

The liver and kidneys are responsible for clearing medicine from the body, which means that if any of these organs are impaired, they cannot remove the medication as effectively, allowing it to remain in the body for longer.


The standard dose for hydroxyzine can differ based on your reason for taking it. Since how much hydroxyzine you are prescribed to take can affect how long it will take your body to remove it, your reason for taking hydroxyzine can then influence how long it remains in your system.

For those taking hydroxyzine for its allergy relief abilities, the standard dose is 25 mg, often taken 3 to 4 times per day. In comparison, those taking hydroxyzine for anxiety often take 50 to 100 mg up to 4 times per day.

Based on these numbers, those who take hydroxyzine for anxiety can be expected to keep the drug in their system for longer than those taking it for allergy relief since there is more of the drug in their system and, thus, more for the body to remove.

Along these same lines, the frequency at which someone takes hydroxyzine can also influence how long it stays in your system. Those taking it for anxiety can take it up to 4 times a day, but someone taking it only two times a day will have less in their system than someone taking it four times a day if they both take the same dose.

Metabolic Rate

Another determinant of how fast your body removes a drug from your system is your metabolic rate, which refers to how quickly your body can break down what has been consumed. Regarding medication, a faster metabolic rate equates to a shorter duration of the medicine in your body. This is because a faster metabolic rate means that your body can break down the medication faster than someone with a slow metabolic rate can.

Metabolic rate often declines as we get older, which is one reason why those who are older can expect to have hydroxyzine in their system for longer.

Body Mass

Generally, those who weigh more and are bigger can expect the drug to remain in their bodies longer.

Overall Health

In terms of your health, those with poorer health often have a harder time removing the drug from their system, causing it to remain for longer inside the body. Furthermore, as mentioned previously, particular health concerns, such as problems affecting the kidney and liver, which are responsible for detoxing the body, can significantly increase the amount of time it takes to remove hydroxyzine from your system.

How Long Does It Take for Hydroxyzine to Wear Off?

The reduction in allergic symptoms, including itching and redness, from hydroxyzine can often last up to four days, at which time its effects will diminish.

Still, while these effects can last up to four days, the peak effectiveness for both allergies and anxiety is often around 2 hours and it generally lasts 3-4 hours. Because of this, hydroxyzine is often prescribed to be taken every 6-8 hours, but it is always important to follow the prescription instructions given to you by your doctor.

How Quickly Does Hydroxyzine Start Working?

Hydroxyzine comes in many forms, including tablets, capsules, suspensions, or syrups, and it is often taken three or four times a day.

Hydroxyzine begins working quickly, often showing its allergy relief effects just 15 to 30 minutes after being taken. Because hydroxyzine works quickly, it is often a favorable medication for acute allergy reactions. However, drowsiness from hydroxyzine can last for 4 to 6 hours. 

Those taking hydroxyzine for its sedative effects generally notice its influence 30 to 45 minutes after taking it. If you are using hydroxyzine as a sleep aid due to sleep problems from stress or anxiety, taking it directly before bedtime is recommended to see the maximum effect.

What Are the Side Effects of Hydroxyzine?

Because of the way that hydroxyzine impacts the brain, one of its most common side effects is drowsiness.

Other possible side effects of hydroxyzine include:

  • constipation
  • dry mouth
  • confusion
  • headache
  • dizziness

Those at an increased risk of side effects include those who are older and those with certain heart conditions or kidney or liver disorders.

If you have a severe form of any of these symptoms, or they do not go away, contact your doctor.

There are also some potentially serious side effects of hydroxyzine, including seizures and unintentional shaking. If you experience either of these symptoms, call your doctor immediately.

Allergic reactions to hydroxyzine are also possible and may present with a rash, areas of swelling and redness on the skin, pus-filled blister-like sores, or a fever. If you experience these symptoms of an allergic reaction, stop taking hydroxyzine and seek immediate medical attention.

The above are just some of the more frequent side effects reported with hydroxyzine, but it may cause other side effects. So, if you have any problems while taking hydroxyzine, even if it does not match the list above, do not hesitate to talk to a doctor about it.

Drug Interactions

One thing to be aware of with hydroxyzine is that it is not always a good choice for someone, especially if you are taking certain medications or have a specific health condition. By talking with your doctor before taking it, you can prevent serious side effects from occurring.

Some medications which hydroxyzine can interact with include:

  • citalopram and other antidepressants that affect the QT interval
  • antiarrhythmics
  • methadone
  • haloperidol and similar drugs
  • phenytoin
  • central nervous system depressants (e.g., sleep medications, opioids, benzodiazepines)
  • levofloxacin antibiotics
  • blood pressure medications (e.g., angiotensin receptor blockers, ace inhibitors, calcium channel blockers, beta-blockers, diuretics)
  • fluoxetine and codeine

The repercussions of taking hydroxyzine alongside these medications can vary, but some complications include dangerous changes in heart rhythm, breathing problems, and an increase in unpleasant side effects.

Furthermore, it’s not recommended to consume alcohol while taking hydroxyzine as alcohol can increase its side effects.

When to See a Doctor?

It’s recommended to speak to a doctor if you ever have questions about hydroxyzine or the conditions that it may be prescribed to treat. If you suffer from allergies or anxiety, your doctor may recommend hydroxyzine, and they will help you formulate a plan to address your symptoms.

It’s also crucial to seek medical attention if you ever experience any severe side effects from hydroxyzine, such as:

  • skin redness
  • rash
  • seizures
  • blister-like or pus-filled sores
  • fever
  • unintentional trembling, tremoring, or shaking

Hydroxyzine overdose is also possible if you take more than you are prescribed, which can be life-threatening. If you ever take too much hydroxyzine, seek immediate medical attention.

For those looking for a convenient way to speak to their doctor, there’s always DrHouse. With this app, you can meet with an online doctor in just 15 minutes to discuss your symptoms and receive answers to any questions you have about hydroxyzine. With DrHouse, medical help is just a tap on your phone screen away.

Key Takeaways

Hydroxyzine is an antihistamine medication that blocks the action of histamine, making it an effective treatment for both allergies and anxiety. However, as something that affects the central nervous system, one of the most common side effects of hydroxyzine is drowsiness, which can leave some people wondering how long they can expect this side effect to last.

The half-life of hydroxyzine is 20 hours, making the estimated total amount of time that it remains in your system 100 hours. However, despite remaining in the system for a long time, hydroxyzine reaches its peak effectiveness at 2 hours and lasts for about 3 to 4 hours.

Hydroxyzine begins working quickly, often within 15-30 minutes for allergies and 30-45 minutes for anxiety, making it a favorable treatment for those with acute concerns. For those interested in hydroxyzine for allergies or anxiety, an online doctor can discuss if it is a good choice and prescribe this medication.


Content on the DrHouse website is written by our medical content team and reviewed by qualified MDs, PhDs, NPs, and PharmDs. We follow strict content creation guidelines to ensure accurate medical information. However, this content is for informational purposes only and not a substitute for professional medical advice, diagnosis, or treatment. For more information read our medical disclaimer.

Always consult with your physician or other qualified health providers about medical concerns. Never disregard professional medical advice or delay seeking it based on what you read on this website.

If you are experiencing high fever (>103F/39.4C), shortness of breath, difficulty breathing, chest pain, heart palpitations, abnormal bruising, abnormal bleeding, extreme fatigue, dizziness, new weakness or paralysis, difficulty with speech, confusion, extreme pain in any body part, or inability to remain hydrated or keep down fluids or feel you may have any other life-threatening condition, please go to the emergency department or call 911 immediately.



on your schedule

Skip the unnecessary waiting room,
see a board-certified clinician now.

Start an Online Visit
Available in 50 states. No insurance needed.
Screenshot of DrHouse Mobile App: Virtual Doctor Appointment in Progress

Prescriptions as needed
Renew or get a new Rx.

On-demand virtual visits
See a physician 24/7.

24/7 care support
We are here to help you.

  • 1

    Download the DrHouse app.
    Set up your free account in a minute.

  • 2

    Start a visit with an online doctor. Wait time is less than 15 minutes.

  • 3

    Get an Rx from your preferred pharmacy. Pick up a Rx nearby or get it delivered to you.

Download our app
Image of a doctor wearing a white lab coat, representing the DrHouse telehealth service