Fexofenadine — sold in the UK as Allevia, Telfast, and Treathay, and known in the US as Allegra — is widely regarded as a good allergy medication for hay fever and chronic spontaneous urticaria. As a second-generation, non-sedating antihistamine, it selectively blocks H1 histamine receptors to relieve sneezing, itching, runny nose, and watery eyes without the drowsiness associated with older antihistamines. Backed by clinical trial evidence and recommended in UK guidelines, fexofenadine offers once-daily dosing and a favourable safety profile. This article explains how it works, what it treats, its side effects, and how to access it in the UK.

What Is Fexofenadine and How Does It Work?

Fexofenadine hydrochloride is a second-generation antihistamine used to relieve the symptoms of allergic conditions. It is available in the UK under several brand names, including Allevia, Telfast, and Treathay (the US brand name Allegra is not widely used in the UK). Fexofenadine works by selectively blocking H1 histamine receptors — the receptors that, when activated by histamine released during an allergic response, produce familiar symptoms such as sneezing, itching, a runny nose, and watery eyes. By occupying these receptors without activating them, fexofenadine prevents histamine from triggering the allergic cascade.

One of the key advantages of fexofenadine over older, first-generation antihistamines (such as chlorphenamine) is that it is non-sedating in the vast majority of users. This is because fexofenadine has poor penetration of the blood–brain barrier, meaning it acts primarily in the peripheral tissues rather than the central nervous system. As a result, it is far less likely to cause drowsiness than first-generation antihistamines. However, some people may still feel sleepy; if this occurs, you should avoid driving or operating machinery until you know how the medicine affects you.

Fexofenadine is rapidly absorbed after oral administration, with peak plasma concentrations typically reached within one to three hours. Its effects can last for up to 24 hours, which supports once-daily dosing in most adults and children over 12 years. The drug is largely excreted unchanged via the faeces and urine, and it undergoes minimal hepatic metabolism — a property that reduces the risk of drug interactions compared with some other antihistamines.

Sources: EMC SmPCs for fexofenadine 120 mg (Allevia/Treathay) and 180 mg (Telfast); EMA EPAR: Telfast.

What Allergic Conditions Can Fexofenadine Treat?

Fexofenadine is licensed in the UK for the symptomatic relief of seasonal allergic rhinitis — commonly known as hay fever — in adults and children aged six years and over. Seasonal allergic rhinitis is triggered by airborne allergens such as grass pollen, tree pollen, and weed pollen, and affects millions of people in the UK each year. Symptoms typically include nasal congestion, sneezing, itchy or watery eyes, and an itchy throat or palate.

It is important to note that for moderate to severe nasal symptoms, intranasal corticosteroid sprays (such as beclometasone or fluticasone) are considered first-line treatment in line with NICE Clinical Knowledge Summary (CKS) guidance on allergic rhinitis. Oral antihistamines such as fexofenadine are particularly effective for itch, sneezing, and eye symptoms, and may be used alone for mild symptoms or alongside an intranasal corticosteroid for more troublesome disease.

Fexofenadine is also indicated for the treatment of chronic spontaneous urticaria (CSU) — a condition characterised by persistent, itchy hives (wheals) and, in some cases, angioedema, without an identifiable external cause. In the UK, the 180 mg strength is licensed for CSU in adults and adolescents aged 12 years and over. Fexofenadine can help reduce the frequency and severity of episodes, improving quality of life for those affected. NICE and British Association of Dermatology (BAD) guidelines recommend non-sedating antihistamines, including fexofenadine, as a first-line treatment option for urticaria.

Whilst fexofenadine is effective for these licensed indications, it is not specifically indicated for:

• Perennial (year-round) allergic rhinitis caused by dust mites or pet dander — though clinicians may use it off-label in this context, following individual clinical assessment

• Allergic asthma, where inhaled corticosteroids and bronchodilators remain the cornerstone of management

• Anaphylaxis, which requires emergency treatment with adrenaline (epinephrine)

If symptoms are not clearly seasonal or are accompanied by more complex features, a GP assessment is advisable to confirm the diagnosis and ensure appropriate treatment.

Sources: NICE CKS: Allergic rhinitis; EMC SmPCs for fexofenadine 120 mg and 180 mg; BSACI/BAD guideline on chronic spontaneous urticaria.

Effectiveness, Side Effects, and Safety Considerations

Clinical evidence supports fexofenadine as an effective antihistamine for allergic rhinitis and chronic spontaneous urticaria. Multiple randomised controlled trials have demonstrated that fexofenadine 120 mg (for rhinitis) and 180 mg (for urticaria) significantly reduces symptom scores compared with placebo, with an onset of action within one to three hours. Head-to-head comparisons with other second-generation antihistamines such as cetirizine and loratadine suggest broadly comparable efficacy, though individual responses can vary — some patients find one antihistamine works better for them than another.

Common side effects of fexofenadine are generally mild and may include:

• Headache

• Nausea

• Dizziness

• Drowsiness (less common than with first-generation antihistamines)

• Dry mouth

If you experience drowsiness, do not drive or operate machinery. Serious adverse effects are rare. At recommended doses, fexofenadine has not shown clinically relevant QT interval prolongation in studies; however, standard caution is still appropriate in people with known cardiac disease, and you should inform your GP or pharmacist of any heart condition before use.

If you suspect you have experienced a side effect from fexofenadine, you can report it directly to the MHRA via the Yellow Card Scheme at yellowcard.mhra.gov.uk. This helps the MHRA monitor the safety of medicines in the UK.

An important drug interaction to be aware of involves fruit juices — particularly grapefruit, orange, and apple juice. These can reduce the bioavailability of fexofenadine by up to 36%, potentially diminishing its effectiveness. Fexofenadine should be taken with water rather than fruit juice. Additionally, antacids containing aluminium and magnesium hydroxide may also reduce absorption if taken simultaneously; a gap of at least two hours is recommended. Erythromycin and ketoconazole can increase fexofenadine plasma levels; inform your GP or pharmacist if you are taking either of these medicines.

From a safety perspective, fexofenadine is generally well tolerated and has a favourable profile compared with first-generation antihistamines, particularly regarding sedation and anticholinergic effects.

Sources: EMC SmPC: Fexofenadine (safety, adverse effects, interactions); NHS medicines information: Fexofenadine; EMA EPAR: Telfast.

Who Should Avoid Fexofenadine or Seek Medical Advice First?

Whilst fexofenadine is considered safe for most adults and children over six years of age, certain groups should exercise caution or consult a healthcare professional before use.

Hypersensitivity: Fexofenadine should not be taken by anyone with a known allergy to fexofenadine hydrochloride or any of the excipients listed in the product's patient information leaflet.

Pregnancy: Human data on the safety of fexofenadine in pregnancy are limited. Where antihistamine treatment is considered necessary during pregnancy, loratadine or cetirizine are generally preferred as first-line options, as they have a more established safety record in humans. Fexofenadine should only be used in pregnancy if clearly necessary and under medical supervision. Speak to your GP or midwife before taking any antihistamine during pregnancy.

Breastfeeding: It is not known whether fexofenadine is excreted in human breast milk. Breastfeeding mothers are advised to seek GP or pharmacist guidance before use.

Renal impairment: Fexofenadine is primarily renally excreted. In patients with moderate to severe kidney disease, reduced clearance may lead to drug accumulation. Patients with renal impairment should consult their GP or pharmacist and follow the advice in the product's SmPC before taking fexofenadine.

Older adults: Older people may be more susceptible to side effects; a GP or pharmacist should be consulted if there is any uncertainty.

Children under six years: Fexofenadine tablets are not licensed for children under six years of age. A paediatrician or GP should be consulted for advice on suitable alternatives.

When to seek emergency care (call 999):

• Signs of a severe allergic reaction or angioedema with difficulty breathing or swallowing — this is a medical emergency

• Sudden swelling of the lips, tongue, or throat

When to seek routine GP review:

• Symptoms that are severe, worsening, or not responding to antihistamine treatment

• Urticaria (hives) that persists for more than six weeks, which warrants assessment to exclude underlying causes

• Symptoms that could suggest a more serious underlying condition

Patients taking other medications — including erythromycin or ketoconazole — should inform their GP or pharmacist before starting fexofenadine.

Sources: EMC SmPC: Fexofenadine (special populations, contraindications); NHS medicines information: Fexofenadine (pregnancy and breastfeeding).

Accessing Fexofenadine in the UK: Pharmacy and Prescription Options

In the United Kingdom, fexofenadine is available in different strengths with different legal classifications, and it is important to understand which applies to you.

• Fexofenadine 120 mg (for seasonal allergic rhinitis in adults and children aged 12 and over) is classified as a Pharmacy (P) medicine — it can be purchased without a prescription from a registered pharmacy. UK brands include Allevia and Treathay.

• Fexofenadine 180 mg (for chronic spontaneous urticaria in adults and adolescents aged 12 and over) is a Prescription-Only Medicine (POM) in the UK and requires a prescription from a GP or other prescriber. The brand Telfast is available at this strength.

• Fexofenadine 30 mg (for children aged 6 to 11 years with seasonal allergic rhinitis) is also a Prescription-Only Medicine (POM) and must be prescribed by a clinician.

Generic fexofenadine products contain the same active ingredient as branded versions and are therapeutically equivalent; generic options are often more cost-effective.

The NHS does not routinely prescribe antihistamines for hay fever on an NHS prescription for adults, in line with NHS England guidance on medicines that should not routinely be prescribed in primary care for self-treatable conditions. Patients are generally encouraged to purchase the 120 mg strength over the counter from a pharmacy. However, prescription access may still be appropriate for:

• Children who require specific formulations or the prescription-only 30 mg strength

• Patients with complex or severe allergic conditions, including those requiring the 180 mg strength for CSU

• Those who require higher doses or combination therapy under specialist supervision

For ongoing or poorly controlled allergy symptoms, a GP referral to an NHS allergy clinic may be warranted. Allergy specialists can offer comprehensive testing, and for refractory CSU, step-up options such as up-dosing of non-sedating antihistamines or biologic therapy (e.g., omalizumab) may be considered in line with BSACI and BAD guidance. The British Society for Allergy and Clinical Immunology (BSACI) provides patient resources and a directory of accredited allergy services across the UK.

In summary, fexofenadine is a well-evidenced, generally well-tolerated antihistamine that represents a sound first-line option for many people managing hay fever or chronic spontaneous urticaria in the UK. Always read the patient information leaflet supplied with your medicine and speak to a pharmacist or GP if you have any questions.

Sources: EMC SmPCs for fexofenadine 120 mg and 180 mg; MHRA reclassification information; NHS England guidance on items which should not routinely be prescribed in primary care; BSACI/BAD urticaria guidance.

Frequently Asked Questions