Antihistamines are “controller” drugs that block the action of histamine, a chemical released during allergic reactions. Histamine contributes to symptoms such as sneezing, runny nose and itchy eyes. 

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

• Drowsiness. Antihistamines can make many children sleepy. This can affect a child's performance in school.
  
  
• 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. This condition is more likely to occur in children who take antihistamines than in adults. If a child experiences convulsions, 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 drugs or dosage.

Oral histamines are often the first choice for treating children with allergic rhinitis. Over-the-counter oral antihistamines cause drowsiness in many children, and excitability in a small percentage. For this reason, it may be best to restrict a child’s use of over-the-counter antihistamines to bedtime (unless, of course, the child is among those who become excitable after antihistamine use).

Newer prescription antihistamines do not cause drowsiness in most children and may be a good alternative to the sedating over-the-counter (OTC) medications. Examples of antihistamines given to children include:

Allergy medications often combine antihistamines with decongestants. Popular choices include: