Is it safe to use diphenhydramine as a sleep aid? The Risks and Recommendations

October 10, 2025 •

4 min read

Over one-third of US adults report not getting enough sleep, leading many to turn to over-the-counter options. This raises a critical question: is it safe to use diphenhydramine as a sleep aid? While approved for occasional use, experts warn against its long-term safety due to risks like tolerance, dependency, and potential cognitive impairment.

Quick Summary

Diphenhydramine, a common OTC sleep aid, is only recommended for very short-term use due to rapid tolerance and side effects. Prolonged use carries risks like cognitive impairment, especially in older adults, and can lead to psychological dependence. Safer alternatives and better sleep hygiene are often more effective long-term solutions.

Key Points

Not for Long-Term Use: Diphenhydramine, the active ingredient in many OTC sleep aids, should only be used for occasional sleeplessness and not for chronic insomnia.
Tolerance and Dependence: The body quickly develops tolerance, requiring higher doses for the same effect, which increases dependency risk and the likelihood of rebound insomnia upon cessation.
Increased Risk for Older Adults: Anticholinergic effects are particularly dangerous for individuals aged 65 and over, increasing the risk of confusion, falls, and potential cognitive decline, including dementia.
Daytime Side Effects: Common side effects include morning grogginess, dry mouth, blurred vision, and dizziness, which can impair daily activities like driving.
Who Should Avoid It: The elderly, children under 12, pregnant or breastfeeding individuals, and those with certain health conditions like glaucoma or an enlarged prostate should avoid diphenhydramine.
Safer Alternatives Exist: For chronic sleep issues, alternatives such as Cognitive Behavioral Therapy for Insomnia (CBT-I) or improving sleep hygiene are safer and more effective long-term solutions.
Consult a Professional: Always speak with a healthcare provider before using or discontinuing diphenhydramine, especially for underlying sleep problems.

How Diphenhydramine Works as a Sleep Aid

Diphenhydramine is a first-generation antihistamine, the active ingredient found in many over-the-counter (OTC) sleep aids like ZzzQuil and Nytol, as well as allergy medications like Benadryl. Its primary use is to treat allergy symptoms by blocking histamine, a natural chemical in the body that triggers allergic reactions. A side effect of this action is drowsiness, which is why it is marketed as a sleep aid.

Unlike newer, second-generation antihistamines that are less sedating, diphenhydramine easily crosses the blood-brain barrier. Once in the brain, it blocks H1 receptors, leading to its sedative effect and helping to induce sleep. However, this is the same mechanism that causes its many undesirable side effects and makes it unsuitable for long-term use.

The Potential Risks of Using Diphenhydramine

While diphenhydramine may provide some short-term relief for occasional sleeplessness, it is not a cure for chronic insomnia and comes with a host of risks that increase with regular or prolonged use.

Immediate Side Effects

The day after taking diphenhydramine, many people experience a 'hangover' effect. This can include:

Daytime Grogginess: Residual sedation can cause next-day drowsiness and a lack of alertness, which can be particularly dangerous when driving or operating machinery.
Anticholinergic Effects: By blocking acetylcholine receptors, diphenhydramine causes a range of anticholinergic side effects. These include dry mouth, constipation, blurry vision, and difficulty urinating.
Impaired Coordination: Dizziness and poor coordination can increase the risk of falls, especially in older adults.

Long-Term Risks

Nightly use of diphenhydramine carries more significant dangers and is strongly discouraged by medical professionals.

Tolerance and Dependency: The body quickly develops a tolerance to the sedative effects of diphenhydramine. This means the initial dose becomes less effective, leading users to increase their intake, which in turn escalates the risk of side effects and psychological dependency.
Rebound Insomnia: When a person stops nightly use, they often experience rebound insomnia, where sleep problems become even worse than before. This reinforces the cycle of dependency.
Cognitive Impairment and Dementia: In older adults, long-term use of anticholinergic drugs like diphenhydramine is linked to an increased risk of cognitive decline, dementia, and Alzheimer's disease.
Reduced Sleep Quality: Diphenhydramine can interfere with the body's natural sleep architecture, suppressing restorative REM sleep. This can lead to daytime fatigue, even if total sleep time appears adequate.

Who Should Not Use Diphenhydramine?

Certain populations should avoid using diphenhydramine for sleep altogether due to heightened risk. These include:

Adults 65 and Older: The American Geriatrics Society strongly advises against its use in this age group due to increased risk of cognitive impairment, confusion, falls, and a longer drug half-life.
Children Under 12: Diphenhydramine can cause paradoxical effects in young children, including agitation and hyperactivity instead of sedation.
Pregnant or Breastfeeding Individuals: Use during pregnancy or while breastfeeding is not recommended, as the drug can pass into breast milk.
Individuals with Certain Health Conditions: Those with closed-angle glaucoma, enlarged prostate, urinary retention, or chronic lung conditions like emphysema or bronchitis should avoid it unless directed by a doctor.

Diphenhydramine vs. Other Sleep Aids


Feature	Diphenhydramine (Benadryl/ZzzQuil)	Melatonin	Cognitive Behavioral Therapy for Insomnia (CBT-I)
Mechanism	Antihistamine, blocks histamine to induce drowsiness.	Natural hormone, signals body for sleep by regulating circadian rhythm.	Non-pharmacological, changes thoughts and behaviors around sleep.
Effectiveness	Moderate for very short-term, occasional sleeplessness; efficacy wanes quickly.	Varies, effective for jet lag or resetting circadian rhythm.	Highly effective for chronic insomnia, long-lasting results.
Long-Term Safety	Not recommended; risks of dependence, cognitive decline, and side effects increase with use.	Generally safe for short-term use, long-term data limited.	High safety profile; considered the gold standard for chronic insomnia.
Daytime Effects	High risk of morning grogginess and impaired alertness.	Minimal daytime effects reported; can include headaches or vivid dreams.	No daytime sedative effects; often improves daytime functioning.
Dependency	High risk with regular use, leading to psychological and physical dependency.	Non-habit forming.	Non-dependent.

Safer Alternatives for Better Sleep

For those struggling with sleeplessness, especially chronic issues, exploring safer and more sustainable alternatives is crucial.

Sleep Hygiene: Establishing a consistent sleep schedule, creating a dark, quiet, and cool sleeping environment, and avoiding large meals, caffeine, and alcohol before bed can significantly improve sleep quality.
Cognitive Behavioral Therapy for Insomnia (CBT-I): A highly effective, non-drug therapy that helps individuals identify and change the thought patterns and behaviors that contribute to sleep problems. It is considered a first-line treatment for chronic insomnia.
Melatonin: A hormone supplement that helps regulate the body's sleep-wake cycle and can be helpful for issues related to jet lag or shift work. It is generally considered safer for short-term use than diphenhydramine.
Herbal Remedies: Options like chamomile tea or valerian root are sometimes used, though evidence for their effectiveness is less robust than for other methods.

Conclusion: A Short-Term Fix, Not a Long-Term Solution

While diphenhydramine is readily available over the counter, the answer to "Is it safe to use diphenhydramine as a sleep aid?" is complex. For occasional sleeplessness in healthy adults, it can be an option, but only for a very limited duration. The rapid development of tolerance, risk of dependency, and concerning long-term side effects, particularly in older adults, make it a poor choice for chronic insomnia. Safer and more effective alternatives exist, including non-pharmacological therapies and other supplements, that address the root causes of sleep problems without the associated risks. As always, consulting a healthcare provider before starting any new sleep regimen is the best way to ensure your approach is both safe and effective for your individual needs. For more information on drug safety and efficacy, consider consulting reliable sources such as the FDA or clinical practice guidelines from the American Academy of Sleep Medicine.

Frequently Asked Questions

No, it is not safe to take diphenhydramine every night for sleep. The body develops tolerance quickly, and long-term use can lead to dependence, withdrawal symptoms, and serious health risks like cognitive impairment.

Diphenhydramine is only recommended for very short-term use, typically for occasional sleeplessness for no more than 7 to 10 nights. If sleeplessness persists for more than two weeks, you should consult a doctor.

Yes, diphenhydramine is particularly dangerous for older adults (65+). Its anticholinergic properties increase the risk of confusion, delirium, falls, and are associated with a higher risk of dementia with long-term use.

The 'hangover' effect is residual drowsiness that can last into the next day, impairing alertness and concentration. This is a common side effect of diphenhydramine due to its long half-life, especially in older individuals.

Diphenhydramine is a sedating antihistamine with more side effects, tolerance risk, and dependency potential. Melatonin is a hormone supplement that regulates the sleep-wake cycle and is generally safer for short-term use, particularly for issues like jet lag.

Yes, psychological and physical dependency on diphenhydramine is possible with prolonged, regular use. This often begins with increasing the dose as tolerance builds, leading to a reliance on the drug for sleep.

Yes, several non-drug strategies can improve sleep. These include practicing good sleep hygiene, such as maintaining a consistent sleep schedule and creating a calming sleep environment, and pursuing Cognitive Behavioral Therapy for Insomnia (CBT-I).

Key anticholinergic side effects of diphenhydramine include dry mouth, blurred vision, constipation, and difficulty urinating due to its interaction with acetylcholine receptors.