Written by Kevin Hwang, MD, MPH | Reviewed by Katie E. Golden, MD Updated on April 6, 2023
Key takeaways:
- Benadryl (diphenhydramine) affects the body in a few ways. So it actually belongs to two classes of medications: antihistamines and anticholinergics.
- Some research studies suggest that frequent use of anticholinergic medications may increase the chances of developing dementia. But no study has looked specifically at Benadryl.
- Benadryl still has some other side effects that can be harmful for older adults. If you take Benadryl often, talk to your provider about safer medications to help with your symptoms.
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What is Benadryl?
Benadryl (diphenhydramine) is an over-the-counter antihistamine medication. People use this oral medication to help with:
- Seasonal allergies (hay fever)
- Symptoms of the common cold
- Hives or itchy skin
- Motion sickness
Like other first-generation (older) antihistamines, Benadryl can make you very sleepy. For that reason, it’s also used as a sleep aid.
How does Benadryl work?
Benadryl works by blocking the action of histamine. This is a natural chemical in the body that’s released during an immune response. Histamine causes symptoms like itching, sneezing, congestion, and runny nose. So blocking histamine helps relieve those symptoms.
Benadryl is both an antihistamine and an anticholinergic medication. This means that Benadryl also blocks the effect of acetylcholine. This is a chemical in the brain that helps send messages between cells. Blocking acetylcholine can cause temporary drowsiness, confusion, and memory loss. As we’ll cover below, this is a key component of the link between Benadryl and dementia.
What is dementia?
Dementia is a group of conditions that affects brain function — like memory, judgment, problem-solving, and orientation. Dementia impacts someone’s day-to-day life and makes it harder for them to care for themselves. The most common type of dementia is Alzheimer’s disease.
Dementia can make it more difficult to do things, like:
- Remembering people, events, or places
- Finding your way home
- Concentrating on tasks
- Communicating with others
- Solving problems
- Planning actions
- Accomplishing daily tasks
- Organizing things
Some people with dementia also experience:
- Confusion
- Anxiety
- Depression
- Personality changes
- Agitation
What does the research say about Benadryl and dementia?
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 raise a cautionary flag. Let’s take a closer look:
- 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. But 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 it doesn’t necessarily mean that the affected people had dementia. 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:
- 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.
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.
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.
Should you stop taking Benadryl?
The research to date has not definitively proven that Benadryl raises the risk of developing dementia. But Benadryl’s medication class (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.
- Pay attention to the side effects of Benadryl, especially if you’re an older adult. The body responds differently to Benadryl as you get older. And you may develop side effects that were never a problem before.
- Benadryl is not intended to be used as a daily, long-term medication for sleep or other issues. See your healthcare provider if you’re taking Benadryl on a regular basis to help with your symptoms.
The bottom line
Benadryl is both an antihistamine and an anticholinergic medication. Some research suggests that anticholinergic medications can increase the risk for dementia. But the link isn’t totally clear. No studies have found that Benadryl specifically causes dementia.
Still, regular use of Benadryl is not recommended. This is especially true for older adults, who may experience more side effects. If you use it very frequently, talk to your provider about other options to avoid unwanted side effects and decrease any chance (even a small one) of developing dementia.
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