Fexofenadine and cetirizine are both second-generation antihistamines recommended by the NHS for treating hay fever. While they work in similar ways — blocking histamine receptors to reduce allergy symptoms — there are important differences that may make one a better fit for you.
Effectiveness
Both antihistamines are clinically proven to relieve hay fever symptoms including sneezing, nasal congestion, runny nose, and itchy eyes. Head-to-head studies show broadly comparable efficacy, with most patients reporting good symptom control from either medication.
However, some research suggests fexofenadine may have a slight edge for certain individuals, particularly those who find cetirizine less effective over time. If one antihistamine stops working well for you, switching to the other is a common and NHS-recommended strategy.
Speed of Action
- Cetirizine: begins working within 20–60 minutes, with peak effect at around 1 hour
- Fexofenadine: begins working within 1–2 hours, with peak effect at around 2–3 hours
Cetirizine generally acts slightly faster, which may be useful for sudden symptom flare-ups.
Drowsiness and Side Effects
This is where the two differ most significantly. Cetirizine, while classed as a non-drowsy antihistamine, can still cause mild drowsiness in around 5–10% of users. The MHRA advises caution when driving or operating machinery until you know how cetirizine affects you.
Fexofenadine, on the other hand, causes no more drowsiness than a placebo in clinical trials. It is considered the least sedating of all commonly available antihistamines, making it the preferred choice for drivers, students, and professionals who cannot afford any sedation.
Other Side Effects
- Cetirizine: headache, dry mouth, fatigue, and stomach discomfort (uncommon)
- Fexofenadine: headache, nausea, and dizziness (uncommon)
Both medications are generally well tolerated and serious side effects are rare.
Cost and Availability in the UK
Cetirizine is one of the cheapest antihistamines available, with packs of 30 tablets costing as little as £1–£2 from UK pharmacies and supermarkets. Fexofenadine 120mg (Allevia) is available over the counter but typically costs £5–£10 for a similar supply. Higher-strength fexofenadine (180mg) requires a prescription.
Which Should You Choose?
Choose cetirizine if you want an affordable, fast-acting antihistamine and are not prone to drowsiness. Choose fexofenadine if avoiding drowsiness is your top priority, or if cetirizine has not fully controlled your symptoms. Consult your pharmacist if you are unsure.