Does Benadryl Make You Sleepy?

benadryl uses and side effects

Key takeaways: 

  1. Benadryl (Diphenhydramine) is an antihistamine and antiemetic medication used and prescribed for allergy reactions along with cough and nausea. Its onset of action in the body is 15 to 30 minutes, while it stays for 6-8 hours maximum in the body. 
  2. Benadryl is taken by insomniacs for its side effects of causing sleep and drowsiness. It should be noted that it’s not prescribed for insomnia and only for allergy symptoms. It’s good to get a medical consultation as well as a prescription for its use, either for allergies or insomnia. 
  3. Benadryl’s common side effects include dizziness, drowsiness, headache, and dry mouth, while serious side effects are dementia, confusion, seizures, and decreased memory.


Benadryl (Diphenhydramine) is a  medication that belongs to the antihistamine and antiemetic drug class. It is mostly prescribed and taken over-the-counter medications for its uses in treating allergy symptoms, its potential to induce sleep and its effects on histamine receptors in the brain. It has a rapid onset of action for about 15 to 30 minutes and will stay in the body for a good 6-8 hours on maximum. It should be noted not to take this medication persistently for longer periods of time. It shows some of the common and serious side effects, including nausea, dizziness, drowsiness, and long-term effects on the brain.

What is Benadryl?

Benadryl belongs to a class of drugs called Antihistamines, 1st Generation, and Antiemetic Agents and is used to provide allergy relief and treat allergy symptoms such as sneezing, runny nose, hives, skin rashes, watering eyes, and other cold or allergy symptoms. It is also used to treat motion sickness, induce sleep, and treat specific symptoms of Parkinson’s disease. Benadryl may be prescribed but is generally sold over-the-counter (OTC) and diphenhydramine in its generic form.

Can Benadryl Help You Sleep?

Yes, it can. Not all,  but most of the antihistamines have the side effect of making the person drowsy and sleepy. Benadryl (Diphenhydramine) can also cause drowsiness as a side effect and is used widely for this effect. People suffering from insomnia take Benadryl as an effective treatment, not for allergies. It should be noted that even if it might give you sleepiness, it shouldn’t be taken persistently for insomnia. 

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An analysis of randomized controlled studies by NIH from the last 12 years indicates that widely used over-the-counter (OTC) sleep aids, particularly diphenhydramine, do not have strong clinical evidence to support their effectiveness and safety.

It’s good to get yourself checked by the healthcare provider for an effective alternative to the medication for insomnia.

Why Does Benadryl Make You Sleepy?

When the allergy reaction in the body gets triggered, histamine is released persistently along with the allergy symptoms, including runny nose and itching. Histamine, as a hormone, keeps the mind and person active throughout the day, making it difficult for a person to sleep. When antiallergy medicine is taken, especially Benadryl (diphenhydramine), it blocks the histamine receptors present in the brain, causing the opposite effect, making the person sleepy. 

Histamine is not only released when there is an allergic reaction in the body; it is released from time to time in reaction to different triggers, making the brain active. People suffering from insomnia have more histamine release in their body, for which they take Benadryl, which helps them go to sleep for longer than usual by blocking the brain’s histamine receptors.

How Long Does Benadryl Take to Work?

Benadryl (diphenhydramine) takes approximately 15 to 30 minutes to reach its maximum effect and to make the other person sleepy. However, its life span in the body is about 4 to 6 hours, which makes it stay in the body for longer periods. 

People taking Benadryl specifically for insomnia take it in the evening time to get a full night’s sleep. It’s important to practice caution while taking any medication. 

It’s crucial and necessary to consult your healthcare provider as this medication is not specifically for insomnia or sleep induction and should not be taken on a regular and long-term basis.

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Is it OK to Take Benadryl to Sleep?

No, It’s not. This medication is not generally prescribed for sleep or insomnia. It is an antihistamine prescribed for allergy reactions and symptoms, says Dr. Richard Honaker, M.D.  It is used for sleep induction in patients suffering from insomnia for its effect of causing drowsiness and dizziness.  

How Much Benadryl is OK to Take As a Sleep Aid?

Benadryl is an antihistamine drug, and it is not prescribed for sleep. However, one of its side effects is causing sleep and drowsiness in people taking this medication. People suffering from insomnia also take this medication as an aid in sleeping. 

The dose mostly used for insomniacs is 30mg, 30-40 minutes before sleep or in the evening, says Dr. Richard Honaker, M.D. However, it’s not okay to take any dose of Benadryl (diphenhydramine) as an aid to sleep better as it is not prescribed for insomnia. 

As per the study conducted by NIH, Long-term usage of Benadryl (diphenhydramine), an antihistamine and non-benzodiazepine sedative-hypnotic, warrants caution due to its potential link to an elevated risk of dementia.

Benadryl is not for insomnia; talk to the virtual doctor now for the right prescription.

Benadryl Over Dosage

Benadryl (Diphenhydramine), if taken more than its optimum maximum dosage of 300 mg/day for adults, might cause some unfavorable side effects, including blurred vision, tachycardia, heart rhythm problems, extreme dizziness, dry mouth, and irritability. As per Dr. Richard Honaker, M.D., “It’s always good to seek medical attention for the correct dose, dosage, time interval between medications, and frequency to save yourself from overdose side effects.” 

Side Effects of Using Benadryl for Sleep

Benadryl can cause mild or severe side effects depending upon the usage. Moreover, the undermentioned list contains some of the critical side effects. Therefore, this list may not include all possible side effects.

A recent study published by NIH found that using certain strong anticholinergic medications for an extended period is linked to a higher risk of dementia. These medications include tricyclic antidepressants, bladder antimuscarinics, and older antihistamines.

Additionally, you can get more information on the possible side effects or tips on how to deal with them by talking with our doctors.

Common Side Effects

  • Sleepiness
  • Weakness
  • Dizziness
  • Headache
  • Dry mouth

Note: Some of the above effects leave in a couple of weeks. 

Serious Side Effect

  • Dementia
  • Confusion
  • Seizures
  • Decreased memory
  • Impaired thinking
  • Fast heartbeat

Long-term side effects

Over-the-counter Benadryl is only approved for temporary or short-term use and isn’t recommended for long-term use. Some side effects that may occur after long-term use are:

  • Memory problems and dementia (especially in seniors)
  • Anxiety
  • Blurred vision
  • Dependence
  • Constipation
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Talk to Your Doctor

Insomnia can affect your ability to work effectively, decreasing your overall productivity, and needs to be treated appropriately. Allergy symptoms can also be very irritating and disrupt your overall health. It’s good to consult a healthcare provider for both of the medical conditions and get the prescriptions as needed to avoid self-medication and its side effects.

FAQs About Benadryl Answered By your Doctor Online Team

What are the long-term side effects of Benadryl on the brain?

Dementia, Hallucinations, Restless legs syndrome, Memory problems, and Anxiety are some of the long-term effects of Benadryl (diphenhydramine) on the brain if taken in extreme doses or for longer periods of time.

How long does Benadryl’s drowsiness last?

It usually takes 4-6  hours for Benadryl’s drowsiness to last after its onset in the body. On maximum, it will stay for 8 hours, and you might experience drowsiness the next day if you take Benadryl at night.

How often can you take Benadryl?

Benadryl (Diphenhydramine), when taken for the allergy, should only be taken with the healthcare provider’s instructions. In general, it’s prescribed to be taken every 4 to 6 hours and should not exceed six doses altogether in 24 hours, says Dr. Richard Honaker, M.D.
Getting a medical consultation and prescription for the correct dosing regimen as per your condition is good.

What not to take with Benadryl?

One of the common side effects of Benadryl is causing drowsiness and dizziness. If this medication is taken with hypnotics or sedatives, It will increase the sleeping effect of the medication, causing extreme drowsiness.

Does Benadryl help with cough?

Yes, it does. Benadryl (Diphenhydramine) is considered an antitussive (cough suppressant) along with an antihistamine by the Food and Drug Administration (FDA) in the United States. It will suppress and enhance the cough properties.

Your Doctors Online uses high-quality and trustworthy sources to ensure content accuracy and reliability. We rely on peer-reviewed studies, academic research institutions and medical associations to provide up-to-date and evidence-based information to the users.

  1. Ozdemir, Pinar Guzel, et al. “Assessment of the effects of antihistamine drugs on mood, sleep quality, sleepiness, and dream anxiety.” International journal of psychiatry in clinical practice 18.3 (2014): 161-168.
  2. Can, I. “Does Benadryl help with or cause anxiety?.”
  3. Borniger, Jeremy. “Messing with the ‘Flip-Flop’Switch: Why Getting Sick Makes You Sleepy.”
  4. Kay, Gary G. “The effects of antihistamines on cognition and performance.” Journal of Allergy and Clinical Immunology 105.6 (2000): S622-S627.


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