Parents ask UK pharmacies every day which antihistamine is safe for a child with hay fever, hives, a rash after an insect bite, or a reaction to something unidentified. The answer is not one-size-fits-all. The three most commonly used oral antihistamines — cetirizine, loratadine and chlorphenamine — each have different minimum ages and different profiles.

This is the age-limit map UK pharmacists work from, drawing on the British National Formulary for Children (BNFc), product licences and NHS patient information.

Why sedating antihistamines are avoided under two

The oldest class of antihistamines — chlorphenamine, promethazine, diphenhydramine — crosses the blood-brain barrier freely and causes sedation. In very young children the effect is unpredictable, can include paradoxical agitation, and has historically been linked to respiratory depression. Neither UK regulators nor NICE recommend sedating antihistamines in children under 2 in almost any situation; promethazine is specifically contraindicated under 2 on the licence.

The modern preference for under-twos is a non-sedating oral antihistamine with a paediatric licence, or, more often, non-drug management plus review if symptoms persist.

Cetirizine — the earliest non-sedating option

Cetirizine oral solution is licensed in the UK from 1 year of age. BNFc dosing:

• 1–2 years: 250 micrograms/kg twice daily
• 2–6 years: 2.5 mg twice daily (or 5 mg once daily)
• 6–12 years: 5 mg twice daily (or 10 mg once daily)
• 12 years and over: 10 mg once daily

Cetirizine is technically "non-sedating" but has the most residual drowsiness of the second-generation group. In practice some parents find it helpful for children whose itch is disturbing sleep; others switch to loratadine if drowsiness is unwanted during the day.

Loratadine — licensed from two

Loratadine oral solution is licensed from 2 years. BNFc dosing:

• 2–12 years (under 30 kg): 5 mg once daily
• 2–12 years (30 kg and over): 10 mg once daily
• 12 years and over: 10 mg once daily

Loratadine is generally considered the least sedating of the routinely stocked paediatric non-sedating antihistamines. It is a reasonable first choice for ongoing hay-fever cover in school-age children.

Fexofenadine — school age and above

Fexofenadine is licensed from 6 years for allergic rhinitis (30 mg twice daily) and 12 years for urticaria (120 or 180 mg once daily depending on indication). It has moved to pharmacy-only status in the UK in recent years and is available without prescription in some formulations, but for paediatric use below 12 a prescription remains the usual route.

Chlorphenamine — sedating, short-term, 1 year+

Chlorphenamine (Piriton) syrup is licensed from 1 year. BNFc dosing:

• 1–2 years: 1 mg twice daily
• 2–6 years: 1 mg every 4–6 hours, max 6 mg/day
• 6–12 years: 2 mg every 4–6 hours, max 12 mg/day
• 12 years and over: 4 mg every 4–6 hours, max 24 mg/day

Chlorphenamine is useful where sedation is acceptable or desirable — severe itch at night, acute urticaria, insect bite reactions — and for acute allergic reactions where a rapid onset matters. It is not a maintenance choice for daytime hay fever.

Promethazine — from two, but rarely first choice

Promethazine is contraindicated under 2. Between 2 and 5 the dose range is narrow and the sedation is deep. Outside of specialist-led paediatric use (e.g. anxiolysis or sleep in specific contexts), UK pharmacies do not typically recommend promethazine for routine allergy symptoms in young children.

A practical UK pharmacy ladder

For common indications:

Hay fever

• Under 1 year: non-drug management; saline nasal irrigation; GP review if bothersome
• 1–2 years: cetirizine oral solution if needed
• 2+ years: loratadine oral solution as maintenance; cetirizine as alternative
• 6+ years: add intranasal corticosteroid (e.g. fluticasone nasal spray)

See our hay-fever antihistamines comparison for the broader breakdown.

Urticaria and itch

• Under 1 year: refer rather than medicate at the counter
• 1+ year: cetirizine or chlorphenamine; chlorphenamine preferred if sleep is the main target
• Chronic urticaria: loratadine maintenance, with cetirizine for breakthrough itch

Insect bite reactions

• 1+ year: chlorphenamine short-term for itch; topical antihistamine creams are no longer first-line (NICE CKS)
• Severe swelling, systemic symptoms or suspected anaphylaxis: 999

When the pharmacy should not dispense

• Child under 1 year (except under specialist direction)
• Child unwell in a way that does not fit a simple allergy pattern — fever, lethargy, breathing difficulty
• Suspected anaphylaxis — 999 immediately; the counter has no role
• Children on other sedating medications or with neurological conditions affecting seizure threshold (chlorphenamine in particular)

Quick-reference table

UK pharmacies have a narrow but useful set of options for children's allergy symptoms. The age limits are not arbitrary — they reflect the available licensing data and the real-world risk profile in small children. When in doubt, the safer answer at the counter is usually referral.

Sources

• BNFc — Cetirizine, Loratadine, Chlorphenamine, Promethazine, Fexofenadine monographs
• NHS — Antihistamines

General information for UK pharmacy customers. Individual paediatric dosing should be confirmed with your pharmacist or GP.