Benadryl (diphenhydramine) is used for allergies and allergic reactions, as well as common cold symptoms. It may cause mild or serious side effects, such as sleepiness and seizures, among others.
Benadryl is available as a prescription and an over-the-counter (OTC) medication. It helps reduce symptoms of hay fever (nasal allergies), other allergies, and colds. Examples include a runny nose and sneezing.
This drug is also used to treat certain allergic reactions, such as swelling and hives. For these purposes, the OTC version of Benadryl can be taken by adults and children ages 6 years and older.
The active ingredient in Benadryl is diphenhydramine. (An active ingredient is what makes a drug work.) The drug comes in many different forms. Some you take by mouth, such as tablets or liquid solutions. Others you apply to your skin, such as creams or gels.
Keep reading to learn about the common, mild, and serious side effects that Benadryl can cause. For a general overview of the drug, including details about its uses, see this article.
Some people may have mild or serious side effects during their Benadryl treatment. Examples of a few of Benadryl’s more commonly reported side effects include:
- sleepiness
- dizziness*
- headache
- blurry vision*
- low blood pressure
* To learn more about this side effect, see the “Side effects explained” section below.
Examples of mild side effects that have been reported with Benadryl include:
- sleepiness
- dizziness*
- headache
- low blood pressure
- constipation
- dry mouth or nose
- blurry vision*
In most cases, these side effects should be temporary. And some may be easily managed. But if you have any symptoms that are ongoing or that bother you, talk with your doctor or pharmacist.
Benadryl may cause mild side effects other than the ones listed above. For more information, talk with your doctor or pharmacist.
* To learn more about this side effect, see the “Side effects explained” section below.
Serious side effects that have been reported with Benadryl include:
- changes in blood cell levels, such as a decreased red blood cell level
- heart rhythm problems, including a condition called long QT syndrome
- seizures
- hallucinations (seeing or hearing something that’s not really there)
- memory loss or dementia*
- feeling confused
- allergic reaction*†
- fast heartbeat*
If you develop serious side effects while taking Benadryl, call your doctor right away. If the side effects seem life threatening or if you think you’re having a medical emergency, immediately call 911 or your local emergency number.
Note: The Food and Drug Administration (FDA) tracks side effects of medications. If you’d like to notify the FDA about a side effect you’ve had with Benadryl, visit MedWatch.
* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after using Benadryl. But it’s not clear whether this side effect occurred in studies.
The side effects of Benadryl in children are generally similar to the drug’s side effects in adults. But it’s also possible for this medication to cause hyperactivity and excitability in children.
Benadryl typically should not be used in children younger than age 6 years because they can have more serious side effects from the drug. This includes seizures and a fast heartbeat.
The OTC forms of Benadryl are approved only for children ages 6 years and older, as well as adults. If your child is younger than age 6 years, talk with their doctor about whether Benadryl is safe for them.
Get answers to some frequently asked questions about Benadryl’s side effects.
Are there any long-term side effects of Benadryl?
Yes, there are. Some long-term side effects that Benadryl may cause include:
- dementia
- memory problems
- anxiety
- dependence or withdrawal* symptoms, such as psychosis, when you stop taking Benadryl
Benadryl is recommended only as a short-term treatment for people with symptoms of allergies or other conditions that the drug treats. If you take Benadryl long term, you may develop long-term side effects of the medication.
Which side effects you experience can determine how long your side effects last. For example, if you feel sleepy, this side effect may last a few hours or until the medication is no longer in your body. But other side effects can be longer lasting.
Talk with your doctor about your Benadryl use and which other medications may be better for your condition.
* With dependence, your body needs the drug to feel like you usually do. With withdrawal, you experience uncomfortable symptoms after stopping a drug that you’ve become dependent on.
Do seniors have a higher risk of side effects from Benadryl?
Yes, older adults (ages 65 years and older) likely have a higher risk of side effects from Benadryl than younger adults. This is because their bodies may get rid of the drug more slowly.
Older adults may have more side effects from Benadryl, including sleepiness, dizziness, or heart problems. Sleepiness and dizziness can increase the risk of falling, which can be very serious.
If you’re an older adult interested in taking Benadryl, talk with your doctor. They may recommend that you take a lower dose of Benadryl to reduce your risk of side effects. Or they may suggest that you take a different medication to treat your allergy or cold symptoms.
Can Benadryl be used in babies or toddlers? If so, what are the possible side effects?
OTC forms of Benadryl should not be used in babies or toddlers. This is because children younger than age 6 years old have an increased risk of side effects from Benadryl.
Children can have the same side effects of Benadryl as adults, such as dizziness or drowsiness. But Benadryl can also cause more serious side effects in children, such as a fast heartbeat or seizures. The drug may also cause children to become more excitable or hyperactive.
You should never use Benadryl to help your child fall asleep. This can be very dangerous.
Due to these risks, you should not give Benadryl to your baby or toddler without the direction of their doctor. If your child has symptoms of an allergy or cold, talk with their doctor about the best way to treat those symptoms.
Does Benadryl cause side effects in dogs?
Possibly. If your veterinarian recommends giving Benadryl to your dog, be sure to discuss possible side effects to watch for and the correct dosage. The dosage may be based on how much your dog weighs, to reduce the risk of side effects.
Benadryl is not approved to be used in dogs, but a veterinarian may recommend it in some cases. It’s important to talk with a veterinarian before giving any medication to your pet. They can recommend whether Benadryl is safe for your dog and which dosage to give.
Does my risk of side effects from Benadryl vary, depending on the dose (such as 25 mg or 50 mg)?
Yes, your risk of side effects can vary, depending on the dose of Benadryl you take.
A higher dose of Benadryl can increase the risk of side effects. So you’re more at risk of side effects from taking 50 milligrams (mg) of Benadryl than from taking 25 mg.
If you have concerns about side effects from your dose of Benadryl, talk with your doctor.
Does Benadryl cause diarrhea?
No, you shouldn’t have diarrhea from taking Benadryl. In fact, Benadryl can cause constipation.
Some other medications used to treat allergy symptoms, such as Allegra Allergy (fexofenadine), may cause diarrhea.
If you have diarrhea while taking Benadryl, talk with your doctor about what may be causing it.
Learn more about some of the side effects Benadryl may cause.
Fast heartbeat
A fast heartbeat is a common side effect of Benadryl. In rare cases, it can become serious.
Symptoms of a fast heartbeat may include:
- feeling like your heart is racing
- dizziness
- shortness of breath
What might help
If you have symptoms of a fast heartbeat while taking Benadryl, talk with your doctor. They may recommend that you take a lower dose of the medication to treat your symptoms. Or they may recommend a different medication for you.
Blurry vision
Benadryl works by drying out your body, which may result in blurry vision. This is a more common side effect of Benadryl.
What might help
If you have blurry vision from taking Benadryl, talk with your doctor or pharmacist. They can recommend ways to decrease this side effect. They may also suggest a different medication to treat your symptoms.
Until your vision has cleared, you should not drive a car or operate other machinery.
Memory loss or dementia
Taking Benadryl may cause memory loss or dementia. Although rare, this side effect may be more common in older adults or people who’ve taken the drug long term. Symptoms can include:
- trouble speaking or finding the right words to say
- problems with short-term memory
- trouble concentrating
What might help
If you’re experiencing memory loss or dementia while taking Benadryl, talk with your doctor. They’ll likely suggest that you stop taking Benadryl. They’ll also look for the cause of your memory loss or dementia so that they can recommend the right treatment for you.
Dizziness
Dizziness is a common side effect of Benadryl. This side effect can be serious.
Until you know how Benadryl will affect you, you should not drive a car or operate other machinery after taking the drug. If it causes you to feel dizzy, avoid doing either activity until the effects of the medication have worn off.
In addition, dizziness may lead to an increased risk of falling for older adults. Falls can be very dangerous for people who are older.
What might help
If you have dizziness from taking Benadryl, talk with your doctor. They’ll recommend that you do not drive a car or operate other machinery while you’re dizzy.
In addition, they may suggest a different medication for your symptoms, one that doesn’t make you dizzy.
Allergic reaction
Like most drugs, Benadryl can cause an allergic reaction in some people. But it’s not clear whether this side effect occurred in studies.
Symptoms can be mild or serious and can include:
- skin rash
- itchiness
- flushing (temporary warmth, redness, or deepening of skin color)
- swelling under your skin, typically in your eyelids, lips, hands, or feet
- swelling of your mouth, tongue, or throat, which can make it hard to breathe
What might help
If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They can suggest treatments to manage your symptoms.
If your doctor confirms that you had a mild allergic reaction to Benadryl, they’ll decide if you should continue using it.
If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.
If your doctor confirms that you had a serious allergic reaction to Benadryl, they may have you switch to a different treatment.
Keeping track of side effectsDuring your Benadryl treatment, consider keeping notes about any side effects you’re having. Then, you can share this information with your doctor. This is especially helpful to do when you first start taking new drugs or using a combination of treatments.
Your side effect notes can include things such as:
- what dose of drug you were taking when you had the side effect
- how soon after starting that dose you experienced it
- the specific symptoms of the side effect
- how it affected your daily activities
- any other medications you were also taking
- any other information you feel is important
Keeping notes and sharing them with your doctor will help them learn more about how Benadryl affects you. And your doctor can use this information to adjust your treatment plan if needed.
Benadryl may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before you take Benadryl. The list below includes factors to consider.
Dementia: Benadryl may cause dementia, as well as worsen symptoms of dementia in a person with this condition. If you have dementia, talk with your doctor before you take Benadryl. Your doctor may recommend that you take a different medication instead.
Allergic reaction: If you’ve had an allergic reaction to Benadryl or any of its ingredients, you should not take it. Ask your doctor what other medications are better options for you.
Heart problems or high blood pressure: Benadryl can increase your heart rate and may cause more serious heart-related side effects, such as heart rhythm problems. If you already have heart disease, taking Benadryl can make your condition worse. Talk with your doctor about whether it’s safe for you to take Benadryl.
Liver problems: Benadryl is removed from your body through your liver. If your liver isn’t working properly, it may take your body longer to remove the medication. This can increase your risk of side effects. If you have any liver conditions, tell your doctor before taking Benadryl.
Kidney, bladder, or prostate problems: Benadryl may decrease the amount of urine that you make. If you have kidney or bladder problems, you may already produce a decreased amount of urine. If you have prostate problems, you may have urinary retention (not being able to fully empty your bladder). These conditions may worsen due to Benadryl. If you have kidney, bladder, or prostate problems, talk with your doctor before you take this drug.
Respiratory conditions, including asthma: Benadryl works by drying out your nose and mouth, which decreases symptoms of an allergy or a cold. This can make mucus in your nose or mouth thicker. If you have trouble breathing, thickened mucus can make it even harder for you to breathe. Before you start taking Benadryl, talk with your doctor if you have any respiratory conditions.
Certain eye conditions: Benadryl may increase pressure in your eyes. If you already have a condition that increases eye pressure, taking Benadryl may worsen your condition. An example of this type of condition is glaucoma. Talk with your doctor to see if it’s safe for you to take Benadryl with your eye condition.
Alcohol use and Benadryl
You should not drink alcohol while you’re taking Benadryl. Alcohol can increase your risk of drowsiness or dizziness. It may also cause more serious side effects, such as trouble breathing or slowed breathing.
If you drink alcohol, talk with your doctor about other medications you can take to treat your cold or allergy symptoms.
Pregnancy and breastfeeding while taking Benadryl
It’s usually safe to take Benadryl during pregnancy. Benadryl doesn’t seem to increase the risk of fetal harm.
And taking small doses of Benadryl for a short time may be safe while breastfeeding. However, Benadryl does pass into breast milk, and it can also decrease milk supply.
If you’re breastfeeding and you take high doses of Benadryl, it may increase your child’s risk of side effects. This is also the case if you take the drug long term.
High doses or long-term use of Benadryl may also reduce your supply of breast milk.
If you’re pregnant or planning to become pregnant, talk with your doctor about the safety of Benadryl treatment during pregnancy. Also talk with your doctor about this if you’re breastfeeding or planning to breastfeed.
Most side effects of Benadryl are mild, and some people may not have any side effects at all from it. In some rare cases, the drug can cause serious side effects.
Before you take Benadryl, be sure to talk with your doctor about whether the drug is safe for you. Some questions that you may wish to ask about Benadryl’s side effects include:
- How can I lower my risk of side effects from Benadryl?
- How long can I take Benadryl for my condition without increasing my risk of side effects?
- If I have serious side effects from taking Benadryl, what other medications can I use instead?
To learn more about Benadryl, refer to these articles:
- Benadryl (diphenhydramine)
- Benadryl Interactions: Alcohol, Medications, and Others
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Q:
Do other medications that I’m taking increase my risk of side effects from Benadryl?
Anonymous
A:
Yes, they may. When taking Benadryl with certain medications, your risk of side effects is increased. Examples of such medications include:
- anticholinergics, such as Ditropan XL (oxybutynin)
- antidepressants, such as Celexa (citalopram) and Zoloft (sertraline)
- benzodiazepines, such as Xanax (alprazolam) and Ativan (lorazepam)
- opioids, such as Zohydro (hydrocodone) and Roxicodone (oxycodone)
Before taking Benadryl, talk with your doctor or pharmacist. Based on other medications you may be taking, they can tell you whether your risk of side effects will increase from taking Benadryl.
The Healthline Pharmacist TeamAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.
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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.
