Key takeaways

  • Benadryl (diphenhydramine) treats allergy and cold symptoms like a runny nose and sneezing, plus allergic reactions such as hives and swelling. Common side effects include sleepiness, dizziness, headache, and blurry vision.
  • Rare, serious side effects can include seizures, heart rhythm problems, hallucinations, and memory loss or dementia — especially with long-term use or in older adults. Higher doses increase the risk of side effects.
  • Children younger than 6 years should not use over-the-counter Benadryl due to increased risk of serious side effects like seizures and a fast heartbeat. Talk with a healthcare professional if you have heart, liver, kidney, or respiratory conditions before taking Benadryl.

Benadryl is available as a prescription and an over-the-counter (OTC) medication for adults and children ages 6 years and older. It helps reduce symptoms of hay fever (nasal allergies), other allergies, and colds.

Like any medication, Benadryl can cause some side effects that may be mild or serious. Keep reading to learn more about these effects and how to manage them.

Side effects are possible with any medication. Benadryl is generally considered very safe and effective, which is why it’s often available OTC. But you may be wondering what side effects you’re most likely to experience while taking Benadryl.

Examples of a few of Benadryl’s more commonly reported side effects include:

Many of these side effects will be mild or go away on their own with time. But if you have any concerns about the side effects you’re experiencing, reach out to a healthcare professional.

Examples of mild side effects that have been reported with Benadryl include:

In most cases, these side effects should be temporary and 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.

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Serious side effects with Benadryl are rare, but possible. Some of the serious effects that have been reported with Benadryl include:

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.

Experiencing side effects? After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you develop a side effect while taking this drug and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

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.

You should never use Benadryl to help your child fall asleep. This can be very dangerous.

Yes, there are. Some long-term side effects that Benadryl may cause include:

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.

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.

Yes, Benadryl may lead to insomnia in some cases.

Benadryl is typically associated with causing drowsiness or sleepiness, but it may sometimes stimulate your nervous system and make it more difficult to fall asleep. However, this is very rare.

Learn more about managing some of the side effects Benadryl may cause.

Drowsiness

Drowsiness is a common side effect of Benadryl. If you experience sleepiness while taking Benadryl, you may consider taking the drug before bed to stop you from feeling groggy during the day. Doctors also recommend avoiding alcohol while taking Benadryl, as this can make drowsiness worse.

Blurry vision

Benadryl works by drying out your body, which may result in blurry vision. This is a more common side effect of Benadryl.

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:

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.

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.

Keeping track of side effects

During 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
  • allergic reaction
  • heart problems or high blood pressure:
  • liver problems
  • kidney, bladder, or prostate problems
  • respiratory conditions, including asthma
  • certain eye conditions

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.

Benadryl is generally considered safe and effective, but like any medication, it may cause some side effects. Its most common side effects tend to be mild and easily managed, including drowsiness and headaches.

If you think you’re experiencing severe side effects from Benadryl, contact a healthcare professional right away.

Disclaimer: While Healthline strives for factual, comprehensive, and current information, this article is not a substitute for a licensed healthcare professional’s expertise. Always consult a doctor before taking or discontinuing any medication. Drug information is subject to change and may not cover all uses, directions, precautions, warnings, interactions, reactions, or adverse effects. The lack of a warning does not guarantee a drug’s safety, effectiveness, or appropriateness for all patients or specific uses. Learn more about our approach to content integrity.