Benadryl and allergic rhinitis: what patients should know

Benadryl is a brand name used for allergy medicines, and the active ingredient can differ by country or product. Check the package rather than relying on the brand name alone. Products containing diphenhydramine can cause marked sleepiness and may not relieve nasal blockage as well as they relieve itching or sneezing.

Diphenhydramine blocks histamine, a chemical involved in allergy symptoms. It can also cause a dry mouth, blurred vision, constipation, difficulty passing urine or impaired coordination. Older adults may be more prone to confusion, dizziness and falls. Some children become restless rather than sleepy.

Drowsiness can continue after the obvious allergy relief wears off. Do not drive, operate machinery or combine it with alcohol or other medicines that make you sleepy. Taking several cold or allergy products together can accidentally duplicate the same ingredient.

Read the active-ingredient panel and follow the product directions. Ask a pharmacist before use if you are pregnant or breastfeeding, or if you have glaucoma, urinary problems, breathing disease, or take sedatives. For symptoms that recur frequently, discuss a less-sedating antihistamine or a nasal treatment designed for ongoing control.

Reduce exposure to known triggers where practical and use saline nasal rinsing with sterile, distilled, or previously boiled and cooled water. Medicine works better when the diagnosis and main symptom—itching, discharge or blockage—are clear.

Get urgent help for trouble breathing, swelling of the lips or tongue, fainting, severe confusion, or difficulty waking. Contact a clinician promptly if you cannot pass urine, develop a racing or irregular heartbeat, or have taken more than directed.

Arrange a routine assessment when symptoms keep disrupting sleep or daily activity, when nasal discharge becomes persistently bloody, or when facial pain and fever suggest that something other than uncomplicated allergy may be present.

Bring the package or a photograph of its label. Ask whether its active ingredient fits your main symptom, whether it interacts with your regular medicines, and what non-sedating option would suit repeated symptoms. Mention snoring, wheezing, eye symptoms, urinary difficulty and any next-day drowsiness.