Key takeaways

  • ZzzQuil is an over-the-counter sleep aid containing diphenhydramine, an antihistamine that causes drowsiness. It’s approved for treating occasional sleeplessness in people ages 12 years and older.
  • Common side effects may include drowsiness, dizziness, dry mouth, constipation, and blurred vision. Rare but serious side effects can include allergic reactions, abnormal heart rhythm, and low blood pressure.
  • ZzzQuil is intended for short-term use only. Talk with a doctor if sleep difficulties persist for more than 2 weeks, or if you have asthma, heart disease, high blood pressure, or glaucoma before taking it.

ZzzQuil is an over-the-counter (OTC) nighttime sleep aid. The active ingredient in ZzzQuil is diphenhydramine, which is also the active ingredient in the allergy medication Benadryl.

Diphenhydramine is an antihistamine that people commonly use to treat allergic reactions, itchiness, and hives. The most common side effect of diphenhydramine is drowsiness.

ZzzQuil is a safe and effective medication for treating short-term sleeping difficulties, or insomnia, in people over 12 years old. However, individuals with certain medical conditions, such as asthma and heart disease, should speak to a doctor before taking ZzzQuil.

Let’s take a look at the uses, dosage, and safety of taking ZzzQuil.

The manufacturer recommends using ZzzQuil for relieving occasional sleeplessness. It works by helping to reduce the time it takes for a person to fall asleep.

The active ingredient in ZzzQuil is an antihistamine called diphenhydramine. Antihistamines reduce the effect of histamine, which is the natural chemical that the body produces during an allergic reaction.

Diphenhydramine binds to the histamine-1 receptor in the body. This receptor is present in many areas of the body, including the respiratory tract, abdominal tract, immune cells, and brain.

Some types of antihistamines can affect your brain, causing the side effect of drowsiness. Diphenhydramine is one of these antihistamines.

Like any medication, ZzzQuil may cause side effects in some people. These might be mild or, rarely, they can be serious.

The most common side effects of diphenhydramine include:

Rarely, more serious side effects can occur, including:

Allergic reaction

For some people, ZzzQuil may cause an allergic reaction.

For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.

For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to ZzzQuil, your doctor may recommend taking a different medication instead.

Adolescents and adults can use ZzzQuil. The manufacturer states that children under the age of 12 years should not use this medication.

The recommended dose of ZzzQuil is 50 mg at bedtime when needed, or as a person’s doctor directs. ZzzQuil is available in both liquid and capsule forms.

For the liquid form, a single 50 milligram dose is equal to 30 milliliters, or 2 tablespoons. Liquid ZzzQuil comes with a special cup for measuring out the correct dose.

For the capsule form, a single 50 mg dose is equal to two ZzzQuil capsules. You cannot cut, chew, or split the capsules. You should not take more than 50 mg of ZzzQuil in a single day.

The liquid form of ZzzQuil contains 10% alcohol. ZzzQuil is also available in an alcohol-free liquid solution, which may be more appropriate for adolescents.

The intended use of ZzzQuil is for occasional sleeplessness. The manufacturer recommends that people consult a doctor if they experience sleeping difficulties continuously for more than 2 weeks, as this may be a symptom of a more serious medical condition.

Because ZzzQuil causes drowsiness, it may affect your ability to drive or operate heavy machinery. It is also important to avoid drinking alcohol when taking ZzzQuil, as this can increase drowsiness.

Older adults should use ZzzQuil with caution, as side effects such as drowsiness, dizziness, and low blood pressure can increase the risk of falling.

Taking ZzzQuil may worsen certain medical conditions, including:

Individuals with these conditions should consult their doctor before taking ZzzQuil.

People who experience urinary difficulties while taking ZzzQuil should stop taking the medication and speak to a doctor.

Not everyone can take ZzzQuil. People should not give ZzzQuil to children under the age of 12 years.

The active ingredient of ZzzQuil can pass into breastmilk, so people who are breastfeeding should consult a doctor before taking it. Pregnant people should also seek medical advice before using this medication.

People taking monoamine oxidase inhibitors (MAOIs), which are a type of antidepressant, should avoid taking ZzzQuil or speak to a doctor first. MAOIs can worsen some of the side effects of antihistamines. Speak with a healthcare professional for other possible drug interactions.

Although ZzzQuil contains diphenhydramine, which can help relieve allergy symptoms, it can still cause allergic reactions in some people. Anyone who has previously had an allergic reaction to ZzzQuil or medications containing diphenhydramine should avoid taking it.

Zzzquil is not generally considered addictive at its recommended dose. However, there is a possibility of misuse and dependence with diphenhydramine, particularly at higher doses or if you use it for longer than 2 weeks.

Melatonin is an OTC hormone supplement that can work to help regulate your sleep cycles. Whether melatonin or ZzzQuil is better will depend on your specific situation.

Melatonin may be better for consistent use, whereas ZzzQuil should only be used sparingly. This means ZzzQuil is likely better for occasional sleeplessness, whereas melatonin is used to help with jet lag.

ZzzQuil is a safe and effective medication that can help relieve occasional sleeplessness. However, people should stop using ZzzQuil and see a doctor if sleeping difficulties persist for more than 14 consecutive days.

ZzzQuil is not suitable for everyone. Children under 12 years old should not take ZzzQuil, and people who are pregnant or breastfeeding should speak to a doctor first.

ZzzQuil can also interact with some antidepressants and can worsen certain medical conditions, such as asthma and heart disease. The side effects of ZzzQuil may increase the risk of falls in older people.

ZzzQuil is not addictive at the recommended dosage. However, people who take very high doses of ZzzQuil for a prolonged period may be at risk of becoming dependent.

Disclaimer: While Medical News Today strives for factual, comprehensive, and current drug information, this article is not a substitute for a licensed healthcare professional’s expertise. Always consult a doctor before taking or discontinuing any medication. Drug information is subject to change and may not cover all uses, directions, precautions, warnings, interactions, reactions, or adverse effects. The lack of a warning does not guarantee a drug’s safety, effectiveness, or appropriateness for all patients or specific uses. Learn more about our approach to content integrity.