Snooze University

Can You Take Benadryl for Insomnia?

by Dale Cudmore | Updated: Jan 27, 2023

If you think that Benadryl makes you sleepy, you’re not just imagining things.

It contains an antihistamine that has a main side effect of making you drowsy.

However, that doesn’t mean that Benadryl is a good treatment option for insomnia.

This post summarizes research on the active ingredients in Benadryl to answer questions you may have like:

  • Why does Benadryl promote sleep?
  • How fast do you develop a tolerance to Benadryl?
  • Is it dangerous to take Benadryl regularly?
  • What are better alternatives to Benadryl for insomnia?

Ingredients in Benadryl That Promote Sleep

The main active ingredient in Benadryl is diphenhydramine, which is an antihistamine. There is 25 mg of diphenhydramine per tablet for reference.

While antihistamines are typically taken for allergy relief, many of them (including this one) also cause drowsiness.

All the other ingredients in Benadryl are essentially filler that aren’t known to affect sleep either way:

Carnauba wax, croscarmellose sodium, D&C red no. 27 aluminum lake, dibasic calcium phosphate, hypromellose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, polysorbate 80, titanium dioxide

Note that in the UK, Benadryl contains different antihistamines like acrivastine or cetirizine, but these still cause similar side effects to diphenhydramine.

How Does Diphenhydramine Work?

Diphenhydramine effectively blocks the neurotransmitter histamine, which plays a role in many parts of your biology.

One thing histamine does is trigger an inflammatory response in your nasal mucosa when allergens are detected. This leads to a runny nose, itchiness, and other typical allergic symptoms.

Not surprisingly, blocking histamine relieves these symptoms.

But histamine also plays a role in sleep regulation, and it turns out that downregulating histamine promotes sleep.

You’ll find diphenhydramine in particular in many over the counter products like Tylenol PM, Advil PM, and other cold medicines.

Can Diphenhydramine Help Insomnia?

There is some research that shows that diphenhydramine can improve insomnia symptoms in insomnia patients.

One study split insomnia patients into 3 dosage groups and found very little difference in effectiveness (1):

The general condition of the patients with insomnia was at least “slightly improved” in 62.5% (12.5-mg group), 60% (25-mg group), and 67.4% (50-mg group) after treatment with the test drug for 2 weeks.

Note that there was no control group, so it’s possible the placebo effect played some role.

SummaryThe big takeaway is that while Benadryl may help with insomnia, taking more doesn’t produce a significant improvement in effectiveness.

Side Effects of Using Benadryl for Insomnia

There is a reason that Benadryl is not prescribed by doctors for insomnia.

Sleepiness isn’t the only common side effect of diphenhydramine (2):

  • Sleepiness
  • Drowsiness
  • Unsteadiness
  • Dizziness
  • Headache
  • Attention disturbance

Let’s explore some potential side effects of Benadryl in more detail.

You Can Quickly Develop a Tolerance to Diphenhydramine

Research shows that most people develop a tolerance to diphenhydramine really quickly.

One study found (3):

Both objective and subjective measures of sleepiness showed significantly higher levels on day 1 for diphenhydramine compared to placebo. By day 4, however, levels of sleepiness on diphenhydramine were indistinguishable from placebo.

Even though that earlier study we looked at saw positive effects on insomnia patients after 2 weeks, most of that was likely due to the placebo effect.

Importantly, this tolerance takes a long time to “reset”.

It turns out that using diphenhydramine for sleep is most effective in people who had not recently had it (4):

The hypnotic effect of diphenhydramine hydrochloride was significantly greater in patients who had not been treated previously.

So even if Benadryl improves your sleep for a night or two now, there’s no guarantee that it will have much effect if you come back to use it in another few weeks or months.

Unwanted Cognitive Effects

One study on elderly patients taking diphenhydramine found that they had an increased risk for delirium symptoms including (5):

  • Inattention
  • Disorganized speed
  • Altered consciousness

The severity of the side effects were dependent on the dose (i.e. taking as little as possible is ideal).

Benadryl Causes General Drowsiness

The effects of antihistamines often carry over to the next day.

Taking Benadryl may make you lethargic and drowsy, almost like a hangover.

Not getting enough sleep can of course be bad for your daily life and work performance, but so can these side effects.

Can Negatively Affect Sleep Quality

Just because you fall asleep faster after taking Benadryl doesn’t mean it’s high quality sleep.

Side effects like dizziness, headache, dry mouth, and drowsiness can cause frequent wake-ups during the night and lead to poorer quality sleep.

So even if you sleep 8 hours, it may feel like you slept much less.

How Much Benadryl Can You Take For Insomnia?

If you absolutely need to take Benadryl to deal with insomnia symptoms on a short-term basis, follow the directions on the packaging. Ideally, talk to your doctor first, especially if you are taking other medication.

In general, there is no benefit to taking more than 1 pill of Benadryl about 30 minutes before intending to sleep.

Better Alternatives to Benadryl for Insomnia

If you’ve read up to this point it should be clear that Benadryl is not a viable treatment for insomnia, at best it might help in a pinch on a short-term basis once in a while.

If you want to go with a “natural” over the counter option, see my review of natural sleeping aids to see which ones actually work and are safe.

But if you have chronic insomnia, see a doctor. Insomnia is a serious health threat that can lead to developing life-changing consequences over time if not treated, so do yourself a favor and get professional help.

At the very least, a doctor can prescribe you with more effective and sustainable medication than Benadryl.


  1. Clinical Evaluation of Diphenhydramine Hydrochloride for the Treatment of Insomnia in Psychiatric Patients
  2. Diphenhydramine Side Effects
  3. Tolerance to daytime sedative effects of H1 antihistamines
  4. Clinical Evaluation of Diphenhydramine Hydrochloride for the Treatment of Insomnia in Psychiatric Patients
  5. Cognitive and Other Adverse Effects of Diphenhydramine Use in Hospitalized Older Patients

Medical Disclaimer: The information on is not intended to be a substitute for physician or other qualified care. We simply aim to inform people struggling with sleep issues about the nature of their condition and/or prescribed treatment.

About the authorDale is the founder of Snooze University and a sleep researcher. I overcame my sleep issues and now I'd like to help you do the same by summarizing the latest sleep studies for you.