While the antihistamine is designed for easing allergy symptoms, it has a rep for helping people fall asleep. The only question is... should it really be used for catching zzz's?
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When you're struggling to sleep, you'll likely try anything to help you conk out. And at some point between tossing and turning and staring at the ceiling in angst, you might consider taking a Benadryl. After all, the antihistamine has a rep for making people feel sleepy and it's easy to get (odds are you already have a box in your medicine cabinet), so it might seem like a smart snooze-inducing idea. But is it actually a good idea? Ahead, sleep experts weigh in on the pros and cons of taking Benadryl to sleep.

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Credit: Getty Images

What Is Benadryl, Again?

Benadryl is a brand name for diphenhydramine, an antihistamine. Antihistamines work by blocking histamine — a chemical in the body that causes symptoms of allergies (think: sneezing, congestion, watery eyes) — in the body, according to the U.S. National Library of Medicine. But histamines do more than instigate the scratchy throat and runny nose that plagues many people come spring. Research suggests certain histamines also play a role in regulating your sleep-wake cycle, with these histamines being more active when you're awake. (Speaking of which, is it bad to take melatonin every night?)

But back to Benadryl: The OTC drug is designed to relieve symptoms of hay fever as well as those brought on by an allergic reaction and the common cold. Diphenhydramine can also work against histamines to combat issues such as a cough from minor throat irritation as well as to treat or prevent motion sickness and insomnia, according to the NLM. And on that note...

How Does Benadryl Help You Sleep?

"Histamine is more likely to wake you up," says Noah S. Siegel, M.D., director of the Sleep Medicine and Surgery Division at Mass Eye and Ear. So, "by blocking that chemical in the brain, [Benadryl] is more likely to make you sleepy."

In other words, "by taking away alerting influences on the brain — histamines — the drug can help some people fall asleep easier," explains Christopher Winter, M.D., author of The Sleep Solution: Why Your Sleep Is Broken and How to Fix It. This diphenhydramine-induced drowsiness or, in Dr. Winter's words, feeling of being "sedated" can happen whenever you take Benadryl, including for its on-label use to ease allergy symptoms. And that's exactly why you'll notice the medication's box clearly states that "when using this product marked drowsiness may occur" and cautions against using when driving a car, operating heavy machinery, or in tandem with any other sedatives (e.g. alcohol), sleep medications (e.g. Ambien), or diphenhydramine-containing products (e.g. Advil PM).

Here's the thing: Benadryl might be able to help you fall asleep but it can't necessarily help you stay asleep. What's more, you can really only use this as a sleep aid so many times before your body gets used to it. "Generally, its long-term effectiveness is minimal, and after four or more days of chronic use, it's debatable as to whether it has any effect as tolerance develops quickly," says Dr. Winter. It's not entirely clear why this happens, but research has shown that people tend to develop a tolerance to antihistamines in a short period of time. That can be bad for a few reasons: If you've been relying on Benadryl to help you sleep, it will eventually stop working for you and, more importantly, if you actually need to take Benadryl for an allergic reaction, it might not be effective.

Dr. Siegel agrees that it's not necessarily the most effective sleep aid, pointing out that "it doesn't stay active in the blood more than a few hours."

Pros vs. Cons of Taking Benadryl for Sleep

Pros

Of course, if you're hoping to sleep, the fact that Benadyl can cause drowsiness is a pro. Simply put: "It makes it easier to fall asleep quickly," says Ian Katznelson, M.D., neurologist and sleep specialist at Northwestern Medicine Lake Forest Hospital. If you struggle to actually feel sleepy or unwind at bedtime, this can help, he says.

You can also find Benadryl at pretty much every drugstore, says Dr. Winter. It's also "less dangerous" than benzodiazepines, a class of psychoactive drugs used to treat anxiety or insomnia (including Valium and Xanax) that may cause dependency, or "drinking yourself to sleep." (See also: Signs Your Casual Drinking Could Be a Problem)

While Benadryl isn't usually addictive — especially when you take it in the proper doses (one to two tablets every four to six hours for those age 12 and up for cold/allergy relief) — there's at least one case study of a man who had to be hospitalized after he went through withdrawal while breaking a diphenhydramine addiction.

Cons

First off, the American Academy of Sleep Medicine specifically recommends that you don't treat chronic insomnia (i.e. difficulty falling asleep and staying asleep for months at a time) with antihistamines because there's not enough evidence that doing so is effective or safe. Basically, the country's leading professional organization dedicated to sleep does not want you to do this — at least, not regularly. Also worth noting: Benadryl does not market itself as a sleep aid on its label or website.

When it comes to taking Benadryl for sleep or allergies, there's also potential for some not-so-great side effects, says Dr. Katznelson; these can include mouth dryness, constipation, retaining urine, cognitive dysfunction (i.e. trouble thinking), and risk of seizure if you take too high of a dose. Diphenhydramine can potentially cause nausea, vomiting, loss of appetite, headache, muscle weakness, and nervousness, according to the NLM. And if you hate feeling groggy after a poor night of sleep, you might want to keep this in mind before popping one of the pink pills: "Benadryl has a potential for 'hangover' sedation the next day," says Dr. Winter.

There's also a possibility of developing a "mental dependence" on Benadryl when taken for sleep, adds Dr. Siegel. Meaning, you may get to the point where you feel like you can't fall asleep without taking the antihistamine first. "I would rather people learn sleep techniques," he says, including things like cutting back on your caffeine usage, keeping your room dark, and exercising regularly. And, again, there's a small risk that you might develop a physical dependence (think: addiction) to it.

There's also a potential risk of struggling with memory loss and even dementia, which at least one major study has linked to the long-term use of Benadryl. (Related: Can NyQuil Cause Memory Loss?)

Who Might Consider Taking Benadryl for Sleep and How Often?

Overall, using Benadryl as a sleep aid really isn't something sleep medicine experts recommend. But if you're an otherwise healthy person, you can't sleep one random time, and you happen to have Benadryl handy, Dr. Katznelson says taking the recommended dose should be fine. Still, he emphasizes, "it should not be used on a routine basis and rarely, if at all." (Okay, but what about edibles? Are they the secret to sounder shut-eye?)

"Clear guidelines are lacking," notes Dr. Katznelson. "But in my opinion, the ideal candidate for rare use of Benadryl for insomnia would be under the age of 50 with no other medical comorbidities or problems," such as pulmonary troubles (e.g. chronic bronchitis) or glaucoma. (FWIW, Benadryl is also known to aggravate prostate conditions such as benign prostatic hyperplasia or prostate gland enlargement.

"I really don't recommend using these types of drug more than a couple of times per month," adds Dr. Winter. "There are better solutions to having trouble sleeping. I mean why not just read a book? The fear of 'not sleeping' in the moment is really the problem for most." (See: Could Sleep Anxiety Be to Blame for Your Tiredness?)

The Bottom Line on Taking Benadryl for Sleep

The Food and Drug Administration upholds that diphenhydramine can be used for the occasional trouble falling asleep, but it's not meant to be a regular thing.

Again, if you randomly need help falling asleep and take a Benadryl, you should be okay. But if you find that you're regularly reaching for the stuff when you need to sleep, sleep medicine experts say it's not really great. Instead, they recommend trying to practice good sleep hygiene, such as having a consistent sleep and wake time, avoiding taking long naps during the day, keeping your bedtime routine consistent, spending 30 minutes to wind down at night, staying physically active, and blocking out light and noise in your bedroom.

Dr. Siegel says it's a good idea to seek professional help if you have "consistent" issues falling asleep or staying asleep several times a week and it's interfering with your life. Need something more specific? Dr. Winter says you probably want to see a doctor for your sleep issues, "at the point when you are heading out to buy Benadryl [for sleep]."