Side Effects of Antihistamines
Older ones tend to cause more side effects, particularly drowsiness.
Newer antihistamines have fewer side effects, so they may be a better choice for some people.
Some of the main side effects of antihistamines include:
Dry mouth
Drowsiness
Dizziness
Nausea and vomiting
Restlessness or moodiness (in some children)
Trouble peeing or not being able to pee
Blurred vision
Confusion
If you take an antihistamine that causes drowsiness, do so before bedtime. Don’t take it during the day before you drive or use machinery.