Antihistamine side effects

Older, sedating types are more likely to reduce alertness. Medicines marketed as non-drowsy may still make some users sleepy, especially when combined with alcohol or other sedating medicines.

Sleepiness can be accompanied by slower reactions, poor concentration or unsteadiness. Other possible effects include headache, nausea, constipation, difficulty passing urine and a dry nose or throat. Children may occasionally become restless or unusually excitable rather than sleepy.

The ingredient, dose, formulation, age, kidney or liver function, and other medicines can all shape the response. Cold remedies, sleep aids and travel-sickness products may already contain a sedating antihistamine, so taking them together can duplicate treatment.

Use only the directed dose and check labels for repeated active ingredients. Avoid alcohol, and do not drive, cycle in traffic or operate machinery when sleepy, dizzy or visually affected. Rise slowly if light-headed and sip water for a dry mouth if you have no fluid restriction.

Speak with a pharmacist before switching products or altering the schedule. Mention glaucoma, urinary problems, heart rhythm concerns, pregnancy, breastfeeding, and liver or kidney disease because these can affect which medicine is appropriate.

Seek urgent medical help for trouble breathing, swelling of the mouth or throat, collapse, a seizure, severe confusion, or inability to wake the person normally. Call for advice promptly after a suspected overdose, even if symptoms have not appeared.

Contact a clinician soon for a fast or irregular heartbeat, inability to pass urine, marked blurred vision, persistent vomiting or severe unsteadiness. Mild effects that interfere with daily tasks also deserve a medication review rather than simply being tolerated.

Ask whether your symptom still needs an antihistamine, whether a less-sedating or locally applied option could work, and which other medicines may add to drowsiness or dryness. Describe when the effect starts, how it affects you and every product taken that day.