NewsUK NewsHealthMany Brits rely on this common allergy medication every summer without realising the long-term impact on health14:06, 29 May 2026As hay fever season sweeps across the UK, millions of people are reaching for familiar allergy tablets to deal with sneezing, itchy eyes and runny noses. But some experts have raised concerns over one commonly used medication and its potential link to a serious long-term health condition.‌The drug in question is Benadryl, a well-known antihistamine sold widely in pharmacies and supermarkets. While many people use it safely for short-term relief, research has suggested prolonged use of certain ingredients may be associated with a significantly higher risk of dementia later in life.‌According to the NHS, antihistamines such as Benadryl can be used to treat allergies, insect bites and hay fever symptoms. Some types can also cause drowsiness, with side effects including dry mouth, dizziness and difficulty concentrating.‌The concern centres around older-style antihistamines containing anticholinergic drugs, which work by blocking acetylcholine — a chemical messenger involved in memory and learning.Benadryl products sold in the US commonly contain diphenhydramine, while some UK Benadryl products contain acrivastine or cetirizine, depending on the formulation.‌Research highlighted by Harvard Health found people who used strong anticholinergic drugs for three years or more had a 54 per cent higher dementia risk than those who used them for three months or less. The study, published in JAMA Internal Medicine, examined nearly 3,500 adults aged 65 and older.Harvard Health explained that diphenhydramine — the active ingredient in some Benadryl products — is among the anticholinergic medications linked to the increased risk. Researchers stressed the findings showed an association rather than definitive proof that the medicines directly caused dementia.According to the NHS, older people may be more sensitive to antihistamines and side effects such as confusion or drowsiness. Health guidance also warns some antihistamines can interact with other medicines or worsen certain medical conditions, including glaucoma and urinary retention problems.‌Another Harvard Health report stated that anticholinergic drugs may affect the brain by blocking signals involved in cognition and memory. Experts added that taking several anticholinergic medicines together could further increase the risk.Alzheimer’s Society says more research is still needed to fully understand the relationship between anticholinergic drugs and dementia. However, it advises people concerned about medication side effects to speak with a GP or pharmacist before making any changes.Article continues belowHealth experts stress people should not suddenly stop taking prescribed medication without medical advice. Those needing regular allergy relief may wish to discuss newer non-drowsy antihistamines or alternative treatments with a healthcare professional.Choose Daily Mirror as a 'Preferred Source' on Google News for quick access to the news you value.‌Harvard UniversityThe MedicinesNHSMental healthPrescriptionsAllergiesDementiaHay feverHealthy LifeBody HealthHealth