Antihistamines

Common side effects of antihistamines include drowsiness, dizziness, poor coordination, restlessness, excitability, nervousness, and upset stomach. These problems usually go away as the body adjusts to the drug and do not require medical treatment. Less common side effects, such as dry mouth, nose, and eyes, irritability, difficulty urinating, and blurred vision, also may occur and do not need medical attention unless they do not go away or they interfere with normal activities.

If any of the following side effects occur, check with the physician who prescribed the medicine as soon as possible:

• rapid, irregular, pounding, or fluttering heartbeat
• convulsions
• sweating
• vomiting
• fever
• chills
• fainting
• breathing problems
• hallucinations
• unusual bleeding or bruising
• low blood pressure
• unusual sensitivity to light
• uncontrolled movements

Other rare side effects may occur. Anyone who has unusual symptoms after taking antihistamines should get in touch with his or her physician.