There are several side effects to consider before giving a child an antihistamine. These include:

• Drowsiness. Antihistamines can make many children sleepy. For this reason it may be a good idea to give the drug to children at bedtime.
  
  
• Hyperactivity or jitters. Some children react to antihistamines with varying types of restlessness. Concerned parents should contact their child’s physician to arrange for a dosage or medication change.
  
  
• Seizures. Convulsions are more likely to occur in children who take antihistamines than in adults. If a child experiences a seizure, parents should alert their child’s physician immediately.
  
  
• Nightmares and irritability. These symptoms may appear in varying degrees in some children. Concerned parents can consult with their child’s physician to change medication or dosage.