Is Benadryl® Linked to an Increased Risk of Dementia?
Research suggests a possible link between long-term use of Benadryl® (diphenhydramine) and an increased risk of dementia in older adults, but scientists have not established that Benadryl® causes dementia.1
The concern centers on Benadryl®'s anticholinergic properties, meaning the medication blocks a brain chemical called acetylcholine that plays a key role in memory and thinking. Understanding what the evidence actually shows can help you have a more informed conversation with your doctor about whether Benadryl® is the right choice for you.
What is Benadryl®, and why does it concern researchers?
Benadryl® is an over-the-counter antihistamine medication used to relieve common allergy symptoms such as sneezing, itching, and runny nose. Its active ingredient, diphenhydramine, works by blocking histamine, a chemical the body releases during an allergic reaction.2 Benadryl® has been available without a prescription for nearly 80 years and remains one of the most widely recognized allergy medications in the United States.
The concern about Benadryl® arises from its secondary mechanism. Benadryl® is also an anticholinergic drug, meaning it blocks the activity of acetylcholine, a neurotransmitter (a chemical messenger in the brain and nervous system) that is central to thinking, learning, and memory.3 When acetylcholine is suppressed, people commonly experience short-term effects such as drowsiness, confusion, dry mouth, and blurred vision. That is why Benadryl® labels advise against driving or operating machinery until you understand how the medication affects you.
The longer-term picture is what concerns researchers. People living with Alzheimer's disease consistently show lower levels of acetylcholine in the brain. Some medications prescribed to slow the progression of Alzheimer's disease work specifically by preventing the brain from breaking down acetylcholine. This connection has led scientists to ask whether repeatedly suppressing acetylcholine over months or years could have lasting effects on how the brain stores and retrieves information.
What research says about Benadryl® and dementia risk
A 2015 study published in JAMA Internal Medicine found higher rates of dementia among people who regularly use anticholinergic medications compared to those who do not.
The study followed nearly 3,500 adults aged 65 and older for more than 10 years.1 All participants were free of dementia at the start of the study. Researchers tracked their medication use, including both prescription anticholinergic drugs and over-the-counter products such as Benadryl®. Cognitive function was assessed at enrollment and every two years throughout the study.
By the study's end, 797 participants had developed dementia. Of those, 637 were judged to possibly or probably have Alzheimer's disease. Researchers found a significant association between cumulative anticholinergic drug use and dementia risk. Participants with the highest exposure, equivalent to taking a standard dose daily for three years, were significantly more likely to develop dementia or Alzheimer's disease than those who did not use anticholinergic drugs at all. Participants with lower cumulative exposure also showed elevated risk, though less pronounced.
The study also found that the specific type of anticholinergic medication did not meaningfully change the level of risk, and neither did the timing of use within the study period.
What the study cannot tell us is equally important. Observational studies identify associations; they do not prove cause and effect. People who use anticholinergic medications long-term may carry a higher baseline risk of cognitive decline due to underlying health conditions unrelated to the medications themselves. Researchers acknowledged this limitation and called for additional investigation. The scientific conversation about Benadryl® and dementia remains ongoing, and more research is needed before firm conclusions can be drawn.
Until more conclusive evidence is available, the most practical step any individual can take is an open conversation with their physician about their medication history, overall health, and any personal risk factors for cognitive decline. No one should stop taking a prescribed medication based on this research alone.
Other medications with similar anticholinergic properties
Benadryl® is not the only medication with anticholinergic properties. In fact, there are more than 600 medications that have anticholinergic effects. It is important to know though, that many of these medications are formulated to address specific conditions for which the blocking of acetylcholine is necessary to reduce certain kinds of nervous system activity. In many of these medications, the anticholinergic properties are their main effect, while in others, they are simply a side effect.5 In any event, if you have been prescribed a medication with anticholinergic effects and have concerns about the risks of dementia, it’s important to talk to your doctor because many times the benefits of these medications may outweigh the risks. Some common medications that have anticholinergic properties include:
First-generation antihistamines
These include doxylamine and chlorpheniramine
Tricyclic antidepressants
These include amitriptyline, desipramine, and doxepin
Gastrointestinal antispasmodics
Such as dicyclomine, used to treat irritable bowel syndrome and related conditions
Bladder medications
Such as oxybutynin and tolterodine, commonly prescribed for overactive bladder
Muscle relaxants
Such as orphenadrine
Parkinson's disease medications
such as trihexyphenidyl
Certain antipsychotic medications
Such as quetiapine
Some of these medications carry stronger anticholinergic effects than others. Again, you should always consult your doctor before stopping any medication that has been prescribed for you, or if you have any questions about particular medications.
What you should do if you take Benadryl® regularly
The current research does not conclude that occasional Benadryl® use poses a meaningful dementia risk for most people. The concern is primarily directed at long-term or cumulative use, particularly among older adults. The steps below offer a practical way to take an informed approach.
Talk to your doctor before making any changes
If you use Benadryl® or another anticholinergic medication on a regular basis, bring it up at your next appointment. Your doctor can review your full medication list, consider your individual health profile, and help you weigh whether continued use remains appropriate for you.
Ask about alternatives
Second-generation antihistamines such as loratadine (Claritin) and cetirizine (Zyrtec) are often considered options with a lower anticholinergic burden than diphenhydramine. Non-medication approaches, such as allergen avoidance, nasal rinses, and allergy testing, may also be worth discussing with your doctor or an allergist depending on your symptoms.4
Request a comprehensive medication review
Polypharmacy, the term used when a person takes multiple medications simultaneously, is common among older adults and can increase the risk of drug interactions and compounding side effects. Ask your primary care physician for a full review of your current medications to confirm that each one remains appropriate and necessary for your current health status.
Support your brain health through daily habits
No single lifestyle change guarantees protection against dementia, but research consistently links several practices to better cognitive health over time: regular physical activity, a balanced diet, adequate sleep, mental stimulation, and social engagement. These habits are worth cultivating regardless of your medication history.
Finding relief from allergy symptoms
Since Benadryl® is commonly used to treat allergy-related symptoms, it may be a good idea to consult a physician about the underlying causes of your allergy symptoms, rather than exclusively treating your symptoms with any over-the-counter medication. If you live in North Texas and want guidance on allergy management, medication safety, or brain health, Texas Health can help you find a provider who can offer personalized recommendations based on your unique needs, symptoms and health history. A trusted physician who knows your full health history is the best resource for any medication decision.
Frequently asked questions
Does taking Benadryl® occasionally cause dementia?
Occasional Benadryl® use does not appear to meaningfully increase dementia risk based on current evidence. The research raising concern focuses on long-term or cumulative exposure, particularly among older adults who use anticholinergic medications regularly over months or years. Using Benadryl® periodically for seasonal allergies or a brief sleep disruption is considered meaningfully different from the sustained exposure levels studied in the dementia research. If you are uncertain whether your use is a concern, your physician can help you assess it in the context of your full health history.
Is Benadryl® safe for older adults to use?
Benadryl® carries additional risks for older adults beyond the dementia research. Diphenhydramine's anticholinergic effects can cause sedation, confusion, and impaired balance, all of which pose meaningful concerns for older individuals who may already face a higher risk of falls or existing cognitive vulnerability. Many geriatric care specialists advise older adults to avoid diphenhydramine unless specifically directed by a physician and to ask about alternative medications with a lower anticholinergic burden when possible. If you are an older adult who uses Benadryl® regularly, bring it up with your doctor at your next visit.
How much Benadry® use is considered "long-term" in the research?
Long-term anticholinergic use, as defined in the JAMA Internal Medicine study, refers to cumulative exposure over months or years rather than occasional doses taken as needed.1 The highest dementia risk in that study was observed among participants with exposure equivalent to a standard daily dose taken continuously for three or more years. Occasional use for seasonal symptoms or a short-term sleep disruption falls well below this threshold. If you are uncertain where your use falls, your doctor can evaluate it based on your specific health history.
References
- JAMA Internal Medicine. Cumulative Use of Strong Anticholinergic Medications and Incident Dementia: A Prospective Cohort Study.
- Benadryl®. About Diphenhydramine Hydrochloride HCl: The Active Ingredient in Benadryl®
- Harvard Health. Common anticholinergic drugs like Benadryl linked to increased dementia risk
- Mayo Clinic. Allergy Medications: Know your options.
- Cleveland Clinic. Anticholinergic Drugs