Drowsiness and lightheadedness may impair the ability to drive or operate hazardous equipment. If impaired, then do not drive. The elderly should use these medications with care and watch for side effects. No problems are expected. Children have increased sensitivity to side effects, and the younger the child, the more pronounced the side effects may be.
Children can experience excitability, which is just the opposite of drowsiness seen in adults.
Antihistamines are not recommended during pregnancy unless the benefit clearly outweighs the risk. Although no studies have proven antihistamines cause birth defects in humans, there are animal studies that have shown some birth defects with higher than normal doses. No problems are expected. These medications sometimes increase sensitivity to the sun and sun lamps. Antihistamine users sunburn faster.