What are some of the common side effects observed with antihistamines? March 31, 2020 01:00 Updated DizzinessDry mouthDrowsinessFeeling nervous, excited, or irritableChanges in vision, such as blurry visionDecreased appetite Related articles What are the two types of rhinitis? Can I drink alcohol when I take antihistamines? What over the counter medications are available? What is allergic rhinitis? What are nasal corticosteroid sprays?