Why Does Benadryl Make You Sleepy? Unpacking the Science Behind this Common Side Effect

If you’ve ever reached for Benadryl to combat seasonal allergies or a common cold, you might have noticed an unexpected side effect: drowsiness. The reason behind this sleep-inducing quality lies in the active ingredient of Benadryl, diphenhydramine, an antihistamine also present in various over-the-counter (OTC) sleep medications like Advil PM and Motrin PM.

Diphenhydramine interacts with your body’s natural sleep-wake cycle, making it easier to drift off to sleep. This effect has led many to use Benadryl as a readily available sleep aid. However, it’s important to understand why Benadryl causes sleepiness and whether it’s a suitable long-term solution for sleep problems.

The Science of Sleepiness: How Benadryl Works

Benadryl’s drowsy side effect is directly linked to how it interacts with histamine in your body. Histamine is a chemical messenger involved in numerous bodily functions, including your immune response. When you encounter allergens, your body releases histamine, triggering allergy symptoms like sneezing, itching, and a runny nose. This is where Benadryl steps in as an antihistamine.

Antihistamines like diphenhydramine work by blocking histamine receptors in your body. While this action effectively reduces allergy symptoms, histamine also plays a crucial role in brain function, particularly in regulating wakefulness. Histamine helps keep you alert and awake throughout the day. By blocking histamine, Benadryl essentially dampens this wakefulness signal in your brain, leading to drowsiness and making you feel sleepy.

This mechanism explains why Benadryl is effective at inducing sleepiness, but it also highlights why it may not be the ideal solution for chronic sleep issues.

Benadryl as a Sleep Aid: Is It a Good Idea?

The over-the-counter availability and effectiveness of Benadryl in inducing sleep have made it a popular choice for those struggling with occasional sleeplessness. Antihistamines can indeed be helpful in falling asleep, especially in short-term situations.

However, medical professionals generally advise against relying on Benadryl or similar antihistamines as a long-term sleep aid for insomnia or other sleep disorders. Furthermore, there are specific warnings against its frequent use, particularly for older adults. Medical sources like UpToDate, a resource trusted by healthcare providers globally, emphasize caution regarding the use of Benadryl for sleep, especially in elderly populations.

The Downsides of Using Benadryl for Sleep

While Benadryl can help you fall asleep, it comes with potential drawbacks that make it less than ideal as a regular sleep aid. Diphenhydramine can cause a range of side effects, including:

Nervousness
Dry nose, mouth, and throat
Dizziness
Headache
Nausea
Loss of appetite

Beyond these common side effects, there are other important considerations when using Benadryl for sleep.

It’s crucial to note that Benadryl should not be given to school-aged children or younger without consulting a doctor first. In some instances, children have experienced severe adverse reactions to Benadryl.

Similarly, adults over 65 years of age should consult their healthcare provider before using Benadryl for sleep. Older adults are more susceptible to Benadryl’s side effects, including dry mouth and eyes, difficulty urinating, and confusion. Benadryl use in older adults can also increase the risk of falls.

Healthier Ways to Achieve Quality Sleep

If you’re seeking better sleep without the potential downsides of Benadryl, or if your doctor advises against its use, numerous alternative approaches can promote healthier sleep patterns.

Improve Your Sleep Hygiene

Often, simple adjustments to your daily habits and sleep environment, known as sleep hygiene, can significantly improve your sleep quality.

Maintain a Consistent Sleep Schedule: Go to bed and wake up at the same time each day, even on weekends, to regulate your body’s natural sleep-wake rhythm.
Limit Caffeine Intake: Caffeine’s stimulating effects can linger for up to eight hours. Avoid caffeine in the afternoon and evening to prevent sleep disruption.
Engage in Regular Exercise: Physical activity promotes better sleep, but avoid intense workouts close to bedtime.
Avoid Alcohol Before Bed: While alcohol might initially induce drowsiness, it disrupts sleep later in the night, leading to poorer sleep quality.
Dim the Lights Before Bedtime: Reduce exposure to bright artificial light, including screens from phones and TVs, in the hour leading up to sleep to encourage melatonin production.

Explore Other Sleep Aids

Various sleep aids are available, both over-the-counter and by prescription. While lifestyle changes should be the first step in addressing sleep issues, sleep aids can be beneficial when used in conjunction with improved sleep hygiene. Consulting your doctor can help you determine the most appropriate sleep aid if needed.

When to Seek Medical Advice

If you consistently struggle to fall asleep or if sleep deprivation impacts your daily life, it’s essential to consult your doctor. A healthcare professional can evaluate your sleep difficulties and identify any underlying causes or recommend suitable treatment options.

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Written By

Jay Vera Summer, Staff Writer

Jay Vera Summer is a writer, editor, and wellness coach. She holds a Bachelor’s of Science in psychology and Master’s degrees in both writing and public policy.

Medically Reviewed by

Dr. Anis Rehman, Internal Medicine Physician MD

Dr. Rehman, M.D., is a board-certified physician in Internal Medicine as well as Endocrinology, Diabetes, and Metabolism.

Learn more about our Editorial Team

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