Can I give my child antihistamines?
Drug interaction guide
Originally published 30 Apr 2026
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Antihistamines can affect children differently than adults. While they usually cause sleepiness, they can sometimes cause 'paradoxical excitation,' making a child hyperactive, shaky, or unable to sleep. In very young children (under 6), some older antihistamines can cause serious breathing problems or severe drowsiness.
Why this happens
Children's brains and bodies are still developing. Their metabolism processes drugs at different speeds, and their central nervous system is more sensitive to the effects of these medicines, which can lead to unpredictable reactions.
What you should do
Always check the packaging or speak to a pharmacist to ensure the medicine is age-appropriate. For children under 6, do not give over-the-counter antihistamines for coughs and colds without a doctor's advice. Stick strictly to the recommended dose for the child's age and weight, and never use two different antihistamines at the same time (such as a hay fever syrup and an itch cream).
Important precautions
Children under 2 years old
Sedating antihistamines must not be given to children under 2 years old as they can cause life-threatening breathing difficulties (respiratory depression).
Drowsiness and hyperactivity
While these medicines usually cause drowsiness, they can sometimes cause 'paradoxical excitation' in children, making them unusually hyperactive, agitated, or unable to sleep.
Food and drink warnings
Fruit Juices (Grapefruit, Orange, Apple)
Do not drink grapefruit, orange, or apple juice while taking fexofenadine. These juices can significantly reduce the amount of medicine absorbed by your body, making it less effective at treating your symptoms. Wait at least 2 hours after taking the medicine before drinking these juices.
More about Fexofenadine (Allegra/Telfast)
High-fat meals
Taking fexofenadine with a meal that is very high in fat can reduce how much of the medicine your body absorbs. It is best to take this medicine on an empty stomach or with a light snack.
Using other medicines
Taking multiple medicines? Our Medicines Interaction Checker helps you check whether your prescriptions, over-the-counter medicines, and supplements are safe to take together. Simply search for your medicines to see potential interactions and what to do about them.
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