It’s in your cabinet and it might be increasing your risk of dementia.
Discover what researchers now know about it and why doctors are urging people to rethink its use.
What is diphenhydramine really used for?
Though originally developed to treat allergy symptoms, diphenhydramine has since become a go-to for many other conditions, including motion sickness, cold symptoms, nausea, anxiety, insomnia, and even Parkinson's disease.
It works by affecting your brain
Diphenhydramine is a first-generation antihistamine that not only blocks allergic reactions but also crosses the blood-brain barrier.
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This allows it to alter sleep cycles and suppress cough - but it also interferes with brain function.
Why experts are sounding the alarm
Doctors warn that prolonged use - even at regular doses - can impair memory, cognitive function, and overall mental clarity.
These risks make the drug particularly problematic for long-term use.
Side effects beyond drowsiness
While most users know it can cause sleepiness, other side effects include confusion, dry mouth, constipation, difficulty urinating, and even blurred vision.
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Less common reactions include weight gain and heart rhythm issues.
Higher dementia risk linked to long-term use
One major study found that people who took diphenhydramine daily for three years had a 54 % higher risk of developing dementia.
Similar results have been confirmed in Europe and Canada.
Why older adults are especially vulnerable
As we age, the body processes diphenhydramine more slowly, often keeping it active for up to 18 hours.
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This lingering effect increases the risk of falls, car accidents, and impaired concentration in seniors.
Overdose can be deadly
Ingesting high amounts - intentionally or by mistake - can lead to seizures, hallucinations, coma, or even death.
The FDA has issued multiple warnings in recent years, particularly after viral social media trends encouraged overuse.
Children and vulnerable groups face even greater risks
A dose that might be tolerable for a healthy adult could be dangerous for children or those with medical conditions.
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Symptoms of toxicity have been reported at doses as low as 0.3 grams.
It’s one of the most misused drugs in the U.S.
Experts say many people unknowingly take more diphenhydramine than needed because it appears in so many OTC products - leading to unintentional overdoses and chronic use.
Safer alternatives are widely available
Second-generation antihistamines like Claritin, Zyrtec, and Allegra provide similar relief without the severe brain-related side effects.
These newer drugs don’t cross into the brain, making them a much safer choice.
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Time to rethink your medicine cabinet
Although diphenhydramine is still FDA-approved, many experts recommend limiting its use to short-term or emergency situations.
With so many safer options available, it’s worth reevaluating your go-to remedies.
This article is based on information from National Geographic.