Millions of people across the globe rely on Benadryl, a common over-the-counter allergy medication, for relief from runny noses and itchy skin. However, a fresh wave of scientific evidence is raising serious concern about the long-term safety of its key ingredient, diphenhydramine. A recent study and mounting medical warnings have drawn direct links between regular Benadryl use and a higher risk of developing crippling diseases such as dementia and Alzheimer’s, prompting doctors to urge consumers, including those in Thailand, to reconsider their treatment choices.
This news is especially significant for Thais given the popularity of over-the-counter allergy treatments in the region, frequent self-medication habits, and an increasingly aging society vulnerable to cognitive decline. With dementia emerging as a leading cause of disability and dependency among older persons in Thailand (WHO), the potential implications of the latest research deserve close attention.
Benadryl, whose active ingredient is diphenhydramine, has been available since the 1940s and is well-known for its sedative and antihistamine effects (Wikipedia). However, recent research published in JAMA Internal Medicine tracked over 3,400 adults over the age of 65 and reported that individuals taking at least two doses per week of anticholinergic medications—like diphenhydramine—had a 54% higher risk of developing dementia over a ten-year period compared to those not using such medications. Moreover, the risk of Alzheimer’s disease was increased by 63% among regular users (Daily Mail).
Anticholinergics like diphenhydramine work by blocking acetylcholine, a crucial neurotransmitter for memory, attention, and learning. While these medications are effective at relieving allergy symptoms, blocking acetylcholine has concerning implications for the brain, especially in older adults. Studies have consistently pointed to anticholinergic drugs as a contributor to cognitive impairment and even earlier mortality (PubMed, 2025; PubMed, 2025 systematic review). Notably, in several European countries, first-generation antihistamines like diphenhydramine are restricted or replaced by newer, safer alternatives, highlighting mounting global apprehension.
Leading physicians have echoed these scientific findings. A pediatric specialist at Case Western University cautioned, “There have been several studies over the past decade that show an association between Benadryl and dementia, particularly in older patients. It is not our first option and it has not been for a long while, given the existence of safer and more effective medications.” An allergist at Massachusetts General Hospital added, “If you’re on a deserted island and Benadryl is the only allergy drug available, you should take it. But, in almost every other case, there are safer, better options.”
Even so, occasional use of Benadryl is considered safe by experts, and doctors stress that panic is not warranted for those who have used it intermittently in the past. A UK-based physician offered reassurance: “The risk appears to be more significant when these types of drugs are used frequently and over many months or years, particularly in older adults. Occasional use, such as for a short bout of hay fever, is unlikely to carry the same level of concern.”
Current prescribing practices in Thailand continue to favor classic antihistamines, but second-generation medications such as cetirizine (often branded as Zyrtec) and fexofenadine (widely sold as Allegra) are readily available and considered much safer for most people. In fact, Benadryl’s European versions have already replaced diphenhydramine with newer antihistamines like cetirizine or acrivastine, which present fewer side effects and little to no association with cognitive impairment (Wikipedia).
The manufacturer of Benadryl, Kenvue, asserts that its product is safe when used as directed, claiming, “We are not aware of any studies that show a causal link between labeled use of diphenhydramine and an increased risk of developing dementia. Diphenhydramine is generally recognized as safe and effective by health authorities in the US.” Still, the latest medical reviews argue that, even without a proven direct cause-effect relationship, the weight of evidence supports a cautious approach, especially among seniors and habitual users (World Allergy Organization Journal, 2024).
For Thailand’s older adults and those with family members at risk for dementia, this research is particularly relevant. Alzheimer’s and other forms of dementia are already a growing health burden in the kingdom, affecting at least 700,000 people, and public health campaigns are increasingly focused on identifying and reducing modifiable risk factors. The notion that a trusted, easy-to-obtain remedy might silently raise one’s risk of cognitive decline is a critical consideration for both individuals and healthcare providers.
Thailand’s health authorities have yet to issue fresh guidance specifically targeting the use of first-generation antihistamines, but international practice and guidelines are already shifting. The American Geriatrics Society has long urged avoidance of anticholinergic medications—including diphenhydramine—for elderly patients due to the risk of adverse central nervous system effects (PubMed, 2024). Doctor associations in Europe and North America increasingly recommend the newer, second-generation antihistamines, which provide equal if not superior relief with a much lower risk profile.
In the Thai cultural context, where respecting elders and caring for aging relatives is a core value, these findings add urgency to revisit medication cabinets and urge conversations with medical professionals. Many Thais, familiar with traditions of self-medication and purchasing drugs from local pharmacies, may not realize that what once seemed harmless could pose an invisible threat over time. This is especially vital in rural regions, where doctor’s visits may be infrequent and older individuals may lean on long-standing routines, including the habitual use of products like Benadryl.
The tendency of some consumers to select medications based on brand recognition, past habits, or peer recommendations underscores a classic challenge for public health: bridging the gap between tradition and science. Even as new treatments emerge and evidence of risk accumulates, deeply rooted habits persist. Addressing this, a 2024 article in the World Allergy Organization Journal concluded, “Diphenhydramine, once a pioneering antihistamine, is now overshadowed by second-generation antihistamines with similar efficacy and fewer adverse effects… in its class it is a relatively greater public health hazard. We recommend it should no longer be widely prescribed or continue to be readily available over the counter.”
Looking ahead, experts anticipate additional research on the long-term brain impact of diphenhydramine, especially in Asian populations where genetic, lifestyle, and dietary factors may shape risk in unique ways. In the meantime, public awareness campaigns and pharmacy education could empower Thai consumers to make safer choices and encourage health authorities to review the list of over-the-counter drugs, particularly for those at risk of dementia.
The practical takeaway for Thai readers is clear: occasional, temporary use of Benadryl may still be appropriate, but repeated or long-term use—particularly among older adults—should prompt a discussion with a licensed healthcare provider. For common allergies, consider switching to second-generation antihistamines, which are widely available throughout Thailand and endorsed as first-line treatments. Family members of elderly Thais or people with memory problems should take extra care to review medications and seek out alternatives under medical guidance. Those managing pharmacies or local clinics are advised to stay updated with global best practices and provide clear, accessible information to the community.
If you or an older loved one are using Benadryl or similar anticholinergic medicines regularly, do not panic, but carefully review your medication routine and consult a healthcare professional. In a fast-changing health landscape, staying informed is the best way to protect both mind and body, supporting Thailand’s drive for healthy aging and better brain health for all.
Sources:
- Benadryl linked to crippling DISEASE: Doctors issue warning after shock study | Daily Mail
- Diphenhydramine - Wikipedia
- Dual risk of anticholinergic burden and CSF Alzheimer’s biomarkers: mortality follow-up study | PubMed
- Anticholinergic medications and dementia risk: Systematic review protocol | PubMed
- World Allergy Organization Journal: Clinical perspectives on the use of diphenhydramine (2024)