WHO DO YOU TRUST? –
July 21, 2025 – Benadryl interferes with the brain chemical acetylcholine, which is responsible for attention, concentration and memory, said Dr. Malaz Boustani, a geriatrician and neuroscientist at Indiana University. And an increasing body of research is linking regular use of these drugs to a higher risk of dementia.
In a 2015 study in JAMA Internal Medicine, researchers followed over 3,000 older adults without dementia for seven years and found that frequent long-term use of acetylcholine-blocking drugs was associated with 54 percent higher risk of dementia and 63 percent higher risk of Alzheimer’s disease. Experts say these results don’t prove that Benadryl specifically causes dementia, and it’s not clear whether the risk extends to younger people or even short-term use.
But given the growing body of evidence tying older antihistamines to cognitive decline, Dr. Boustani said he doesn’t prescribe Benadryl.
Diphenhydramine is also found in over 300 different products, including some NyQuil and Tylenol products, so Dr. Boustani recommends that patients read the labels of their favorite allergy, sleep or cold medications — and ask a pharmacist if they’re not sure.
