Yes, Benadryl is an antihistamine that causes drowsiness in most people. Some people use Benadryl for this side effect if they have trouble sleeping (insomnia), but this is not recommended long-term.

The drowsy or sedation effect typically lasts about 8 hours, but may persist into the next day if taken at night. In some people, especially young children, diphenhydramine may lead to a stimulant effect called paradoxical excitation.

Do not drive, operate machinery, or perform other hazardous activities if you experience dizziness or drowsiness while taking Benadryl. Alcohol consumption and use of other medicines that also cause drowsiness may worsen these effects. Use alcohol cautiously if you take Benadryl.

What is Benadryl?

• Benadryl (diphenhydramime) is an over-the-counter (OTC) antihistamine commonly used to treat indoor and outdoor allergy symptoms such as sneezing, runny nose, watery eyes or itchy nose or throat.
• It works by blocking the natural chemical histamine found in the body.
• Diphenhydramine is also used to treat or prevent motion sickness, for hives and itching, and to treat some movement disorder symptoms of Parkinson's disease.

First-generation H1-antihistamines such as diphenhydramine can cause sedation, dizziness and motor coordination impairment and are generally not recommended for long-term treatment of seasonal allergies. Other first generation H1 antihistamines include doxylamine (used as an OTC sleep agent), hydroxyzine and chlorpheniramine.

Other options for seasonal allergies, such as second-generation (non-sedating) H1 antihistamines (example: Allegra, Claritin, Zyrtec) and nasal corticosteroids (example: Flonase) are just as effective and with fewer side effects for long-term treatment of seasonal allergies. Second-generation H-1 antihistamines do not cross into the blood-brain barrier and central nervous system (CNS) as easily as the first-generation H-1 antihistamines.

Learn more: Common Antihistamines Available in the U.S.

Why does Benadryl make you sleepy?

First-generation H1-antihistamines such as diphenhydramine block the histamine-1 receptors in the brain, which can lead to drowsiness. Diphenhydramine also has anticholinergic properties that can lead to sedation and other side effects. Higher doses of Benadryl will increase side effects.

Side effects of Benadryl include:

• dry mouth
• dry eyes
• blurred vision
• constipation
• urinary retention
• drowsiness, sleepiness, sedation
• dizziness
• lack of coordination

How does it come at the store?

Benadryl (diphenhydramine) is available over-the-counter (OTC) primarily as:

• oral tablets
• oral liquid-filled capsules
• oral solutions
• a topical cream, gel or spray

It is also available as an injection (prescription only).

Diphenhydramine is also found in OTC products specifically for use as a sleep aid, such as in Unisom SleepGels and Zzzquil.

It may also be used in combination with other nonprescription medicines specifically for its drowsy effect. For example, Advil PM, Motrin PM and Aleve PM contain an NSAID pain reliever (ibuprofen or naproxen), as well as diphenhydramine, which is used as a temporary nighttime sleep aid.

Generic, brand name and store brands of Benadryl are available. Generic products are typically more affordable.

How much Benadryl do I need to sleep?

The typical recommended adult dose for insomnia is 25 to 50 mg thirty minutes before bedtime for occasional use only. Antihistamines should not be used to induce sleep in children.

Routine use of sedating antihistamines like Benadryl is not recommended by the American Academy of Sleep Medicine and Veteran's Administration guidelines, and other experts, due to a lack of evidence of improvement in sleep quality.

Guidelines state the long-term use of Benadryl (4 weeks or longer) for sleep should be limited to patients who do not have success with non-drug treatments and only when the benefits outweigh the risks. Use of diphenhydramine (Benadryl) for sleep in the elderly (65 years and older) is not recommended due to sedation and anticholinergic side effects.

Drugs with anticholinergic side effects can cause a wide array of side effects, some of which can be serious, including drowsiness or sedation, blurred vision, dizziness and urinary retention.

A study in JAMA Internal Medicine found that 3 years or more use of anticholinergic medications (for example: tricyclic antidepressants, first-generation antihistamines, antimuscarinics used for overactive bladder) was linked with a 54% higher risk for developing dementia than taking the same dose for three months or less. Results also suggested that the risk for dementia with anticholinergics remains even after drug discontinuation.

Learn more: Anticholinergic Drug Side Effects and Safety

Non-drug treatments and changing lifestyle habits that may lead to trouble sleeping should be used initially to help treat insomnia. Simple changes in your daily habits may help. For example, turning off electronics (computers, TVs, video games, smartphones or other screens) at least 30 minutes before bedtime, limiting caffeine/alcohol/nicotine, avoiding naps, or eating heavily late in the evening.

You should contact your healthcare provider if you or your child has long-term problems with getting to sleep or staying asleep.

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How long does the Benadryl drowsiness effect last?

The drowsy effect of a 25 to 50 mg dose can vary, but typically lasts about 8 hours, and may persist into the next day if taken at night. This may affect your ability for safe driving, and your performance at work or at school. Do not drive, operate machinery, or perform hazardous activities if you experience dizziness or drowsiness while taking Benadryl.

Alcohol consumption and combined use of drugs that also cause drowsiness can worsen these effects. Use alcohol cautiously (if at all) if you take Benadryl. Higher doses of Benadryl may worsen side effects.

Have your pharmacist or doctor review for possible drug interactions with Benadryl before you start treatment. Tell them about all of your medicines, including prescription, over-the-counter, vitamins and herbal or dietary supplements.

Does Benadryl make children sleepy or excited?

Benadryl may cause drowsiness in children and teens, but it can also lead to something known as “paradoxical excitation” in some people, including younger children. Paradoxical means the side effect that occurs is opposite to what is normally expected.

• “Paradoxical” excitation” can lead to agitation or trouble sleeping due to nervous system stimulation.
• Researchers are not sure why paradoxical excitation occurs. Some studies have shown that people who break down diphenhydramine (Benadryl) quickly in their body (called “ultrarapid metabolizers”) may be more prone to this reaction.

You should not use diphenhydramine (Benadryl) to help make a child sleepy. Do not give this medication to a child younger than 2 years old. In children 2 to 5 years of age, do not use this product unless directed by a doctor.

Related: Dosage of Benadryl in Children

Always ask your pediatrician or healthcare provider before giving a cough or cold medicine to a child. Death can occur from the misuse of cough and cold medicines in very young children.

How can I prevent insomnia?

To help prevent insomnia, first examine your bedtime routine, caffeine use, and other lifestyle issues. For example, you may want to:

• Keep a regular bed and awake time
• Avoid electronics and blue screen light (TV, phone, computers, tablets) close to bedtime
• Keep the room dark and at a comfortable temperature
• Limit caffeine-containing drinks after lunch and heavy nightime meals
• Skip alcohol at night, which can lead to middle-of-the-night awakenings
• Engage in exercise earlier in the day, rather than late at night or right before bed, if this affects your sleep quality
• Avoid daytime naps
• Read or watch TV in a room other than your bedroom, and not 30 minutes before bedtime. Consider reading a book (not electronic) instead
• Consider sleeping in another bed or room if your partner keeps you awake.

Bottom Line

• Benadryl (generic name: diphenhydramine) is an antihistamine that causes sleepiness in most people. Some people use Benadryl for this effect to help with sleep or insomnia, but this should be short-term. Do not use Benadryl to make a child sleepy.
• Diphenhydramine can also cause "paradoxical excitation", often in young children, instead of drowsiness. Contact your doctor if this occurs.
• Do not drive, operate machinery, or consume alcohol or other sedating drugs if you experience dizziness or drowsiness while taking Benadryl.
• Contact your doctor if you or your child have trouble sleeping.

This is not all the information you need to know about Benadryl (diphenhydramine) for safe and effective use and does not take the place of your doctor’s directions. Review the full product information and discuss this information and any questions you have with your doctor or other health care provider.

References

• Sateia MJ, Buysse DJ, Krystal AD, et al. Clinical practice guideline for the pharmacologic treatment of chronic insomnia in adults: an American Academy of Sleep Medicine clinical practice guideline. J Clin Sleep Med. 2017;13(2):307-349. doi:10.5664/jcsm.6470
• Sicari V, Zabbo CP. Diphenhydramine. [Updated 2022 Jul 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK526010/
• Benson D. Trouble sleeping? Experts say skip antihistamines. Baylor College of Medicine. News. June 28, 2021. Accessed May 2, 2023 at https://www.bcm.edu/news/experts-warn-against-antihistmaines-sleep-aid
• Benadryl Dosage Charts for Infants and Children. Drugs.com. Accessed May 2, 2023 at https://www.drugs.com/dosage-charts/benadryl-infants-children.htm
• de Leon J, Nikoloff DM. Paradoxical excitation on diphenhydramine may be associated with being a CYP2D6 ultrarapid metabolizer: three case reports. CNS Spectr. 2008 Feb;13(2):133-5. doi: 10.1017/s109285290001628x. 
• JM Weiler, Bloomfield J, Woodworth G et al. Effects of fexofenadine, diphenhydramine, and alcohol on driving performance. A randomized, placebo-controlled trial in the Iowa driving simulator. Ann Intern Med 2000; 132:354
• MS Dykewicz, Wallace D, Baroody F et al. Treatment of seasonal allergic rhinitis: an evidence-based focused 2017 guideline update. Ann Allergy Asthma Immunol 2017; 119:489. DOI: 10.1016/j.anai.2017.08.012
• Banerji A, Long AA, Camargo CA Jr. Diphenhydramine versus nonsedating antihistamines for acute allergic reactions: a literature review. Allergy Asthma Proc. 2007 Jul-Aug;28(4):418-26. doi: 10.2500/aap.2007.28.3015.
• Drugs for cough. Issue 1562. The Medical Letter. Dec. 17, 2018. medicalleter.org.

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