Josh Chandler | July 8, 2022

10 Side Effects of Zzzquil

What Is ZzzQuil?

ZzzQuil is an over-the-counter medication used for relieving occasional sleeplessness. It is a drug that does not require a prescription and can be purchased at the local pharmacy. It helps you fall asleep more easily by blocking histamine receptors in the brain. Histamine is a brain chemical that increases alertness, so by blocking the receptors, ZzzQuil promotes drowsiness. It also blocks the acetylcholine receptors in the body, which affect functions like heart rate, attention, and muscle movement, causing the body to relax.


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Zzzquil Side Effects

ZzzQuil, a popular over-the-counter sleep aid, is widely used by individuals struggling with occasional sleeplessness. While it’s effective in inducing sleep, understanding the potential side effects of ZzzQuil is crucial for safe usage. In this section, we’ll dive deep into the various side effects associated with ZzzQuil, helping you make an informed decision about its use.

Common Side Effects: ZzzQuil contains diphenhydramine, an antihistamine that causes drowsiness. While it’s generally safe, some common side effects include dizziness, dry mouth, blurred vision, constipation, and mild drowsiness the next day. It’s important to note that these symptoms are typically mild and subside as your body adjusts to the medication.

Potential Allergic Reactions: In rare cases, users may experience allergic reactions to ZzzQuil. Symptoms can include rash, itching, severe dizziness, and trouble breathing. If you notice any signs of an allergic reaction, seek medical attention immediately.

Long-term Use and Dependence: One of the significant concerns with sleep aids like ZzzQuil is the risk of dependence or tolerance. Prolonged use may lead to reduced effectiveness, necessitating higher doses to achieve the same sleep-inducing effect. It’s recommended to use ZzzQuil only for short-term periods.

Interactions with Other Medications: ZzzQuil can interact with other medications, potentially leading to increased side effects. If you’re taking other prescription drugs or supplements, consult your healthcare provider before using ZzzQuil.

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It is essential to follow the directions on the package because it is possible to become addicted to ZzzQuil. You can also overdose if you take too much, causing serious side effects, including low blood pressure or seizures. Do not use this medication if you are pregnant or breastfeeding. It is crucial to speak with a pharmacist or a healthcare provider if you are considering taking this drug and are already on other medications to ensure no adverse drug interactions that could have serious consequences.


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Is It Ok to Take Sleep Aid Every Night?

Sleep aids are not meant to be taken every night, and Medications like ZzzQuil are recommended for short periods to avoid dependence. Following the dosage instructions on the package and only taking this medication for a maximum of ten days will keep most people safe from misuse and addiction and keep side effects to a minimum. There is also evidence of long-term negative health consequences to taking medications that contain diphenhydramine hydrochloride, including dementia, that can be avoided by using these medications sparingly.

If you are taking sleep medications every night or cannot sleep without them, or if these medications are not helping you achieve a good night’s sleep at the recommended dose, do not increase your dosage. Instead, tell your doctor, as there may be another condition causing your sleeplessness.

Is ZzzQuil Good for Insomnia?

ZzzQuil is a good over-the-counter sleep medication for short-term use, but it is not recommended for insomnia. Call your doctor if your sleeping difficulties last longer than 14 days in a row.

Insomnia is a condition in which a person will have difficulty falling asleep or staying asleep, or they will wake up too early or not feel refreshed when they wake up in the morning. This is often not a problem that sleep aids can solve, and sometimes it may be simple lifestyle adjustments like:

  • Avoiding large meals, caffeine, nicotine, stimulants, and alcohol before bed
  • Exercising during the day a few hours before bedtime
  • Buying a new and more supportive mattress
  • Maintaining the same sleep schedule and practicing “sleep hygiene,” avoiding screens (TVs, phones, etc.) one hour before bed, and keeping the bedroom dark, quiet, and cool.

If these practices do not help, talk to your doctor and check whether it may be underlying health conditions like depression, heartburn, or even heart disease are causing you to stay awake at night. Relying on ZzzQuil nighttime sleep aids will not help you fall asleep or treat insomnia if your restless nights are caused by a physical health issue or your lifestyle and habits.

For information on how to quit Ambien, check out our blog here:


Need Zolpidem for Z’s? How to Quit Ambien and Avoid Ambien Withdrawal

What Are the ZzzQuil Side Effects?

There are several mild and severe side effects of taking ZzzQuil, both short-term and long-term. These include:

Digestive Issues

Because you take ZzzQuil by oral ingestion (through the mouth), the drug goes through your digestive system and may cause stomach upset, loss of appetite, nausea, vomiting, and constipation. You may wish to take this medication with food to ease these symptoms.

Nervous System Issues

ZzzQuil sleep medicine affects the central nervous system, including the brain and spinal cord. This medication causes drowsiness, blurred vision, dizziness, headache, muscle weakness, and excitement. Call your doctor if these side effects bother you or don’t go away.

The effect of diphenhydramine overdose can cause severe drowsiness, tremors, nervousness, feeling unsteady, confusion, seizures, delirium, hallucinations, and coma. For this reason, it is imperative to follow the directions and ask a medical expert for advice on taking ZzzQuil safely.

Respiratory System Side Effects

If taking the medication causes you to feel congestion in your chest or dryness of your throat, mouth, and nose, you can drink water for relief.

Cardiovascular System Effects

Because this medication affects the heart and blood vessels, you may wish to talk to your doctor before taking ZzzQuil, especially if you already have low blood pressure or heart disease. ZzzQuil side effects that may become serious include:

  • Dangerously low blood pressure
  • Lightheadedness
  • Palpitations (heart skipping a beat)
  • High-speed heart rate
  • Arrhythmia (irregular heartbeat)

It is important to sit or lie down if you feel lightheaded while taking ZzzQuil because people fall down when passing out. This will help you avoid hitting your head or injuring yourself while falling.

Vision and Hearing Issues

If you take too much ZzzQuil nighttime, you may experience serious side effects like:

  • Tinnitus (ringing in your ears)
  • Blurry vision or dry eyes

Tell your doctor if you experience any vision or hearing issues while on this medication.  

Urinary Issues

Drugs containing diphenhydramine HCL can negatively affect the urinary system, causing difficulty or pain while urinating.

Allergic Reactions to Taking Sleep Aids

If you experience an allergic reaction when taking this medication, stop taking it immediately and tell your doctor right away.


The effect of ZzzQuil may cause you to experience drowsiness, even during the following day. A standard dose of diphenhydramine can create impairment equivalent to a blood alcohol level of 0.10, higher than most states’ limits for drunk driving. It is important to monitor yourself carefully, as this may affect your ability to drive or engage in activities in which you need to be alert, like operating heavy machinery.


Some people’s reaction to ZzzQuil involves performing actions in their sleep, including walking, eating, driving, or making phone calls while unaware of what they are doing.

Psychological Effects of Sleep Aid Abuse

Other common side effects of these medications include short-term memory loss, problems with concentration, poor focus, anxiety, mood swings, confusion, impatience, and nightmares. Depression and delusions are also common.

Other less common physical effects of taking ZzzQuil are itchy skin, flushed skin, increased body temperature, and restlessness. The Food and Drug Administration (FDA) has found a connection between frequent and long-term use of drugs containing diphenhydramine and the risk of developing dementia, including Alzheimer’s disease, especially in older adults who abuse this medication.


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Can I Get Addicted to ZzzQuil?

It is possible to become dependent on ZzzQuil, especially if you take high doses or abuse it for long periods. This medication was designed to be taken for two weeks or fewer. The active ingredient diphenhydramine releases dopamine in the brain like other drugs, causing sensations of mild euphoria. Eventually, you will become physically dependent on the substance, leading to compulsive use and addiction. You may also find that once you are used to taking ZzzQuil to fall asleep, you will feel unable to sleep without it and may develop withdrawal symptoms when you do not take it.


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Signs of Sleep Aid Addiction

Common signs of sleep aid addiction are:

  • Experiencing cravings for the drug when you do not have access to it
  • Noticing a higher tolerance to the drug, needing to take more to be able to get a good night’s sleep
  • Being unable to or unwilling to quit using the ZzzQuil or other sleep aids after two weeks or longer.
  • Noticing withdrawal symptoms when you try to quit or cut back on taking sleeping pills
  • Buying the drug from different locations to disguise drug use or otherwise being secretive about or hiding your sleep aid use
  • Continuing to take the drug despite harmful consequences to your finances, relationships, work-life, social life, and to your health
  • Making mistakes at work while under the influence or otherwise being unable to function normally due to being exhausted or feeling ill due to diphenhydramine abuse
  • Blowing off social and professional obligations, having functional issues in life due to sleep drug abuse
  • Taking sleep aids for months or years straight and being unable to sleep without taking any sleep aids

Sleep Aid Addiction Treatment

If you relate to the symptoms in this article, it may be time to consider getting addiction treatment for sleep aid dependence. At drug rehab Los Angeles, we can create a comprehensive and individualized program with treatment options to help you with your withdrawal symptoms during your Detox in LA phase. We will work to get you the therapeutic, holistic, and physical care you need to overcome your addiction to sleeping aids and your sleep disorders. Contact us at (800) 426-1818 today to learn more about our inpatient and outpatient programs and how we can help you regain control over your life, body, and sleep schedule.


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Josh Chandler
Josh Chandler
After growing up in Chicago and North Carolina, Josh chose to get help with substance use disorder and mental health in California because of the state's reputation for top-tier treatment. There, he found the treatment he needed to achieve more than five years of recovery. He's been in the drug and alcohol addiction rehab industry for four years and now serves as the Director of Admissions for Resurgence Behavioral Health. Josh remains passionate about the field because he understands that one phone call can alter the course of a person's life.

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