Got some nasty allergies ruining your day? A dose of Benadryl can fight the symptoms away in a matter of minutes. Since some may feel a few side effects after taking them, today we’ll be discussing a frequently-asked question — does Benadryl make you tired?

What Does Benadryl Do?

Benadryl (diphenhydramine) is a brand-name, over-the-counter medication classified as an antihistamine/anticholinergic that relieves allergy symptoms, hay fever, the common cold, and other things like rashes, itching, watery eyes, cough, runny nose, and sneezing. 

Benadryl is readily available in two forms — oral (tablets, liquid-filled capsules (liquid-gels), chewable tablets, and liquid solutions) and topical (creams, gels, sprays, and sticks).

While not directly approved for direct usage, Benadryl is also used as a popular remedy to relieve symptoms of motion sickness like nausea, vomiting, and dizziness. For conditions like nasal congestion and stuffiness, some Benadryl products containing both diphenhydramine and phenylephrine may also help reduce sinus pressure or pain.

Does Benadryl Make You Tired & Sleepy?

Does Benadryl make you sleepy? – The answer is yes. Here’s why:

As an antihistamine, Benadryl can induce drowsiness by working against a chemical produced by the central nervous system (histamine). It can cross the blood-brain barrier and inhibit the excess production of histamine, which plays a role in regulating sleep and wakefulness in the immune system, though sometimes it may also block histamine release in the brain – this disruption of the action of histamines in the brain results in drowsiness.

But that’s not to say it’s a safe sleep-inducing agent. While antihistamines cause sleepiness as a side effect, medical experts discourage using Benadryl as a form of sleeping aid.

Dr. Philip Alapat, assistant professor of medicine at Baylor College of Medicine, says it may yield more disadvantages. Some side effects of antihistamines, such as impaired cognitive abilities, agitation, difficulty in urination, and dry mouth, while generally mild and tolerable, can pose a risk for some people, especially those with underlying conditions and are already in their senior years. 

While it does help induce drowsiness, it doesn’t assure good quality of sleep and may even cause hyperactivity, especially among children. He also adds that using antihistamines can lead to sleepwalking, sleep terrors, and other parasomnias. 

If you’re suffering from sleep problems, consult a doctor or sleep disorders specialist to help treat the problem, which could stem from other conditions like obstructive sleep apnea, circadian rhythm disorders, or depression. 

Both the American Academy of Sleep Medicine and the European Sleep Research Society recommend cognitive behavioral therapy (CBT) for treating sleeping problems. CBT focuses on sleep hygiene, helps adjust the circadian rhythm, and replaces thoughts and behaviors that cause or worsen sleep.

When To Avoid Benadryl

Regarding other uses, the American Headache Society discourages using Benadryl to relieve migraine headaches since they found that it may not actually help improve symptoms. At the same time, they found other medications like sumatriptan and dexamethasone stronger in preventing recurrences. 

Other Side Effects 

Like most medications, Benadryl can occasionally cause a variety of side effects; some may differ depending on the person’s age:

Other more common side effects include: 

  • Dry mouth
  • Weakness
  • Dizziness
  • Headaches

Serious side effects could include the following:

  • Cognitive problems (e.g., impaired thinking, memory loss, confusion, dementia, etc.)
  • Rapid heartbeats
  • Seizures

Regarding cognitive problems, one study found that constant usage of Benadryl (being an anticholinergic drug) increased the risk for dementia and Alzheimer’s disease for up to 20 years after exposure.

Along with cognitive problems, long-term Benadryl usage could yield the following side effects.

  • Constipation
  • Eyesight problems
  • Anxiety
  • Dependence

While some people experience drowsiness or a calming effect after taking Benadryl, others may experience the opposite—Instead of feeling sleepy, they may experience excitation and agitation, worsening anxiety symptoms.

In children, it may cause:

  • Restlessness
  • Constant irritability 
  • Sleeping problems
  • Muscle spasms
  • Seizure

In newborns, oral Benadryl can cause:

  • Breathing problems
  • Seizures
  • Sudden infant death

The over-the-counter forms of Benadryl are only approved for children 6 years and older (and for adults, of course). Despite this, many diphenhydramine overdose cases happen in children younger than 6 years old, with a fatal dose for children estimated to be 500 mg (Death may occur within 2 hours of overdose)


The following medications/drugs have been found to interact with Benadryl, each with varying levels of interaction:

Avoid taking them simultaneously with your Benadryl medication, or take them hours apart from each other to prevent interactions.

The Best Time To Take Benadryl

Since Benadrylrelieves allergies, cold, and cough symptoms, it is usually taken every 4 to 6 hours. When it’s used to treat motion sickness, it is usually taken 30 minutes before moving around and, if needed, before meals. Since it may cause drowsiness, some doctors advise taking them before bedtime.

The body quickly absorbs Benadryl (after oral administration), and its effects are felt within one hour after ingestion, which may last from four to six hours. 


Antihistamines like Benadryl provide quick and effective relief from allergic reactions. While these over-the-counter medications are approved for occasional use in most people, they may cause sleepiness/drowsiness and some side effects. It may even increase the risk for dementia and Alzheimer’s if taken long-term.

If you’re having problems with your antihistamine use, consult a doctor immediately to see if you need to switch treatments. If you have sleeping problems, ask a healthcare professional for safer and more effective methods.

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Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.

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