Does Benadryl Cause Dementia?

Kevin O. Hwang, MD, MPH

Dr. Hwang is an internal medicine physician, primary care provider, and Associate Professor of Medicine at UTHealth McGovern Medical School in Houston.

Media reports have raised interest in whether Benadryl causes dementia. It’s an important question, but the answer isn’t so clear. Should you be concerned about this common medication? Let’s find out.

What is Benadryl?

Benadryl (diphenhydramine) is an oral over-the-counter antihistamine medication. Many people use it for seasonal allergies, also known as hay fever, and to treat symptoms of the common cold. Some also use it to treat hives and motion sickness.

Like other first-generation (older) antihistamines, Benadryl can make you very sleepy. For that reason, it is also used as a sleep aid.

Additionally, Benadryl is classified as an anticholinergic. Other drugs in this class are prescribed to treat mental health disorders and bladder disease.

How does Benadryl work?

Benadryl works by blocking the action of histamine, a natural chemical in your body that is released when you have an allergic response. Histamine causes symptoms like itching, sneezing, congestion, and runny nose. Blocking histamine helps relieve those symptoms.

What is dementia?

Dementia is a loss of mental ability that affects your daily activities. Everybody forgets things once in a while, but dementia impacts routine, day-to-day life. The most common type of dementia is Alzheimer’s disease.

Dementia can make it more difficult for you to do things like:

• Remember people, events, or places
• Find your way home
• Concentrate on tasks
• Communicate with others
• Solve problems
• Plan actions
• Accomplish daily tasks
• Organize things

Some people with dementia also suffer from:

• Confusion
• Anxiety
• Depression
• Personality changes
• Agitation

Why are people worried about Benadryl and dementia?

Researchers are looking for factors that cause or raise the risk for dementia. One of the potential factors is medications.

First-generation antihistamines like Benadryl not only block the effect of histamine, but as anticholinergics, they also block the effect of acetylcholine, a chemical in your brain that helps send messages between cells. Blocking acetylcholine can cause temporary drowsiness, confusion, and memory loss. So, it’s natural to wonder if Benadryl also causes long-term mental problems like dementia.

What does the research say?

Several studies have found a link between anticholinergics and dementia. While the research has not found a definitive link between Benadryl and dementia, the findings do raise a cautionary flag.

• For example, a long-term follow-up study showed that people who took an anticholinergic medication every day for more than 3 years had a significantly higher risk of developing dementia compared to people who did not take them at all. However, the study did not report on individual medications like Benadryl.
• A short-term follow-up study found that people taking anticholinergic medications had signs of brain shrinkage on MRI scans. They also scored lower on mental tests compared to people not taking the medications. These findings point to dementia but don’t necessarily mean that the affected people had The study also didn’t determine which specific medications (such as Benadryl) were linked to the MRI results and test scores.

Other research studies that looked specifically at antihistamines didn’t find an association with dementia.

• For example, a 2019 study found a link between dementia and several classes of anticholinergics used to treat depression, schizophrenia, bipolar disorder, seizures, Parkinson’s disease, and overactive bladder. But there was no association between dementia and antihistamine medications.
• A 2018 study had similar findings. While certain types of anticholinergic medications were linked to dementia, antihistamines were not.

Things to note about the research

These studies have important limitations to be aware of.

First, you can buy many antihistamines, including Benadryl, without a prescription. That means it’s difficult for researchers to know exactly who was and wasn’t taking the medications during the studies.

Second, the studies were observational, which means that the associations between dementia and medications might be explained by other factors.

Could something else be causing the dementia? 

Other factors that were not measured in the studies may have raised the risk for dementia. These factors include genes, certain medical conditions, and environmental exposures.

Some older adults may also take antihistamines to treat symptoms of early dementia, such as trouble sleeping. In that case, taking antihistamines would be (theoretically) a result of dementia rather than a cause of it.

Should I stop taking Benadryl?

The research to date has not definitively proven that Benadryl (as a specific individual medication) raises the risk of developing dementia. However, the class of medications Benadryl belongs to (anticholinergics) does appear to be associated with dementia.

If you take Benadryl, talk to your healthcare provider about whether you should stop taking it, other antihistamines, or other anticholinergics.

If you and your healthcare provider agree that you should keep taking it, you can follow these tips to lower your potential risk of dementia or other complications:

• Take the lowest effective dose for the shortest time for relief of allergy or other symptoms.
• Be aware of your sensitivity to Benadryl, especially if you’re older. People get more sensitive to drugs with age. An older person who’s taking multiple medications or who already has certain medical problems that anticholinergics can worsen (like prostate enlargement) may suffer side effects when taking Benadryl.
• Benadryl is not intended to be used as a daily long-term medication for sleep or other issues. See your health care provider if your symptoms persist.