Antihistamines work for most people with mild allergic rhinitis. When they stop working — or never really worked well — the reason is almost always one of six things. Getting to the right answer changes treatment entirely.
The Six Most Common Reasons
1. Wrong trigger identified
Treating for pollen when your actual trigger is house dust mite, or vice versa. Antihistamines provide non-specific symptom relief — avoidance and targeted therapy require knowing the correct allergen.
2. Non-allergic rhinitis
Up to 50% of chronic rhinitis is non-allergic — triggered by temperature changes, air quality, odours, or hormones. Antihistamines have minimal effect because there's no IgE response driving symptoms.
3. Multiple overlapping triggers
Polysensitisation — allergy to several things at once. One antihistamine managing grass pollen may be overwhelmed during a period of high exposure to a second allergen. The total allergen load determines symptom severity.
4. The wrong antihistamine
Cetirizine, loratadine, and fexofenadine differ in efficacy by individual. Some people respond significantly better to one formulation than another. Most patients have only ever tried one.
5. Not using nasal steroids
For persistent or moderate-severe allergic rhinitis, NICE guidance recommends intranasal corticosteroids as first-line, not antihistamines. Many patients use antihistamines alone when they need both.
6. Nasal polyps or structural issues
Persistent blocked nose that doesn't respond to antihistamines may have a structural cause — polyps, deviated septum, chronic sinusitis. These are non-allergic and require different management.
The Antihistamine Question: Which One to Take
| Antihistamine | Type | Duration | Notes |
|---|---|---|---|
| Cetirizine | Non-sedating | 24 h | Most widely used; some find it slightly sedating |
| Loratadine | Non-sedating | 24 h | Very low sedation; slightly less potent than cetirizine for some |
| Fexofenadine | Non-sedating | 24 h | Least sedating; requires prescription in some dosages |
| Bilastine | Non-sedating | 24 h | Newer; good evidence, minimal sedation, take on empty stomach |
| Chlorphenamine | Sedating (1st gen) | 4–6 h | Useful for acute reactions; not appropriate for daily use |
When Antihistamines Aren't Enough
For moderate to severe allergic rhinitis, the treatment ladder goes beyond over-the-counter tablets:
- Intranasal corticosteroids (e.g., mometasone, fluticasone) — first-line for persistent symptoms; more effective than antihistamines for nasal congestion
- Combination intranasal sprays — antihistamine + corticosteroid in a single spray (e.g., Dymista)
- Montelukast — a leukotriene antagonist sometimes added when antihistamines and nasal steroids are insufficient
- Allergen immunotherapy — desensitisation treatment targeting the specific allergen identified through testing; the only treatment that modifies the underlying immune response
The Value of Knowing Your Exact Trigger
The ALEX3 allergy blood test identifies your specific IgE sensitisations across 300+ allergens — every UK-relevant pollen type, house dust mite species, pet danders, and food allergens. With a precise allergen profile, your GP can distinguish true allergy from non-allergic rhinitis, identify polysensitisation, and target treatment accordingly — including whether allergen immunotherapy is appropriate for your specific sensitisation pattern.
Find Out What You're Actually Allergic To
ALEX3 allergy testing at Lambert Medical Practice. 300+ allergens from one blood draw. Appointments available this week.
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