side effects of antihistamine
Newer-generation antihistamines such as Allegra, Clarinex, and Zyrtec and have fewer side effects, so they may be a better choice for some people. Some of the main side effects of antihistamines include: 1  Dry mouth. 2  Drowsiness.3  Dizziness. 4  Nausea and vomiting. 5  Restlessness or moodiness (in some children).6  Trouble urinating or not being able to urinate. 7  Blurred vision. 8  Confusion.ome of the main side effects of antihistamines include: 1  Dry mouth. 2  Drowsiness. 3  Dizziness. 4  Nausea and vomiting. 5  Restlessness or moodiness (in some children). 6  Trouble urinating or not being able to urinate. 7  Blurred vision. 8  Confusion.