Walk into any UK pharmacy in May and you will find a wall of hay fever antihistamines with confusingly similar branding. The brand names change, but the active ingredients underneath are what matter. This guide explains the three main second-generation antihistamines available in the UK - cetirizine, loratadine, and fexofenadine - and what the evidence says about which suits different sufferers. It is general information only; your pharmacist or GP can advise on the right choice for you.
How Antihistamines Work for Hay Fever
When pollen enters your body, immune cells called mast cells release histamine, a signalling molecule that causes the familiar symptoms: sneezing, itching, watery eyes, and congestion. Antihistamines block H1 histamine receptors, preventing histamine from binding and triggering this response.
Second-generation antihistamines (cetirizine, loratadine, fexofenadine) are generally preferred over older first-generation ones because they cause far less drowsiness. All three are broadly similar in effectiveness for most hay fever sufferers - the differences lie in onset speed, duration, side-effect profile, and individual response. If one does not suit you, a pharmacist can suggest trying another.
Cetirizine: A Fast-Acting Option
Cetirizine 10mg is one of the most widely used hay fever antihistamines in the UK.
- Onset: typically around 1 hour, which is faster than loratadine.
- Duration: 24 hours, taken once daily.
- Drowsiness: a minority of users notice mild drowsiness - the highest of the three second-generation options, though still much lower than older antihistamines.
- Availability: widely available without prescription from pharmacies and supermarkets.
It may suit people who want relatively fast relief and do not find it sedating. If drowsiness is a concern, a pharmacist may suggest taking it in the evening. Always follow the pack instructions or your pharmacist's advice on dosing and suitable ages.
Loratadine: The Least Sedating for Many People
Loratadine 10mg is often chosen by people who need to avoid drowsiness, for example for driving, work, or exams.
- Onset: around 1 to 3 hours.
- Duration: 24 hours, once daily.
- Drowsiness: minimal in clinical trials, statistically similar to placebo.
- Availability: widely available without prescription.
It is a common choice for students during exam season, drivers, and people in safety-critical jobs, and is frequently used for children's hay fever for the same reason. As with any medicine, check suitability with a pharmacist, particularly for children or if you take other medication.
Fexofenadine: A Strong Non-Drowsy Option
Fexofenadine 120mg (available over the counter) is increasingly stocked in UK pharmacies and is regarded as a strong non-sedating option; a 180mg dose is available on prescription for more severe cases.
- Onset: around 1 to 3 hours.
- Duration: 24 hours.
- Drowsiness: among the least sedating antihistamines at standard doses.
- Availability: the 120mg dose is available without prescription; higher doses require a GP prescription.
It may suit people whose hay fever is not well controlled by cetirizine or loratadine, or who find other antihistamines sedating. If over-the-counter options are not enough, speak to your GP about whether a prescription dose is appropriate.
What If Antihistamines Are Not Enough?
For moderate-to-severe hay fever, antihistamines alone often give incomplete relief. Options a GP or pharmacist may suggest alongside them include:
- Nasal corticosteroid sprays (such as fluticasone, mometasone, or beclometasone). NICE guidelines recommend adding one for persistent symptoms, as they reduce nasal inflammation at source and are more effective than antihistamines alone for congestion.
- Eye drops (sodium cromoglicate or antihistamine drops) for eye symptoms that oral antihistamines do not fully control.
- Immunotherapy (allergy desensitisation): the only approach that modifies the underlying allergy rather than managing symptoms. Available on NHS referral or privately, it takes 2 to 3 years but can produce a lasting reduction in sensitivity.
- Air filtration: running a MERV-13 purifier in the bedroom reduces the amount of pollen in the air you breathe overnight, lowering the total allergen load your other treatments have to manage.
The Best Approach: Starting Before Peak Season
A key insight that most over-the-counter advice misses is that antihistamines tend to work better when taken preventively rather than reactively. Once you are already very symptomatic, a large number of histamine receptors are already triggered.
Starting an antihistamine 1 to 2 weeks before your expected pollen trigger - for grass pollen, late April in southern England and early May in the Midlands - gives the medicine time to reach steady blood levels before significant exposure. The same principle applies to nasal steroid sprays, which need 1 to 2 weeks of consistent use to reach full effect. Your pharmacist can advise on timing. Combine an early start with a bedroom MERV-13 air purifier and closed windows at night for the most complete, evidence-supported approach.
Reducing Your Pollen Exposure at Home
Antihistamines address the downstream histamine response, but they do not reduce the amount of pollen entering your airways. Cutting your exposure is a complementary strategy. Keeping bedroom windows closed at night, showering before bed, and running a bedroom air purifier all lower the pollen load your medication has to cope with.
For overnight use, choose a quiet mechanical purifier rather than an ioniser. The CleanAirKits Luggable XL 7-Fan uses a MERV-13 filter (around 93% capture), delivers up to 681 m3 per hour, and runs under 35 dB, so it can clear a bedroom while you sleep. It is Energy Star Most Efficient 2026 rated and costs only a couple of pounds a year in filters to run. Many sufferers find that with cleaner bedroom air they rely on their medication a little less on lower-pollen days - though you should never stop prescribed treatment without checking with your GP.
When to See Your GP Rather Than Self-Treat
Self-treatment with over-the-counter antihistamines is appropriate for mild-to-moderate hay fever. See your GP if:
- Symptoms persist despite regular antihistamines plus a nasal spray.
- Hay fever is significantly affecting your sleep, work, or daily life.
- You have asthma that worsens during pollen season - a marker of poorly controlled combined disease that warrants review.
- You want to discuss immunotherapy as a longer-term option.
Your GP can prescribe higher-dose or prescription-only treatments and refer you to an NHS allergy clinic. Referral waits can be long, so keep any appointment offered even if next season's symptoms seem milder.
