There are three main types of allergy test — and the right one depends on how severe your symptoms are and what you're hoping to find out.
June 2026 · 7 min read · Lambert Medical Clinical Team
If you've been struggling with hay fever and want to get tested, you'll quickly discover there isn't just one type of allergy test. There's the skin prick test your GP might refer you for, a basic blood test, and more detailed molecular tests available privately. Knowing which is appropriate — and when it's worth the extra investment — is not always obvious.
This guide explains the differences between each type, what each one can and cannot tell you, and helps you decide what's right for your situation.
| Your Situation | Test to Consider |
|---|---|
| Mild seasonal symptoms, responding to antihistamines | Standard specific IgE blood test |
| Cannot stop antihistamines (pollen season) | Specific IgE blood test |
| Referred by GP, antihistamines not an issue | Skin prick test |
| Moderate–severe, year-round, or multiple triggers | Molecular allergy test (e.g. ALEX3) |
| Considering immunotherapy (desensitisation) | Molecular allergy test — essential |
| Mouth tingling when eating fruit (oral allergy syndrome) | Molecular allergy test |
The skin prick test has been used for over a century and is the most common allergy test performed in NHS allergy clinics. Small drops of allergen extracts are placed on your forearm, and a lancet is used to gently prick through each drop. If you are sensitised to that allergen, a raised, itchy wheal — similar to a small mosquito bite — appears within 15 minutes.
What it can tell you: Whether your immune system has been exposed to common allergens including grass pollen, tree pollen, house dust mite, pet dander, moulds, and some foods. Results are immediate.
Limitations:
Best for: Initial investigation when referred to an NHS allergy clinic, or when you can comfortably stop antihistamines.
A specific IgE blood test (sometimes called a RAST test, though modern versions use different technology) measures allergen-specific immunoglobulin E antibodies in your blood. A blood sample is taken and sent to a laboratory, where it is tested against a panel of selected allergens.
What it can tell you: Whether you have IgE antibodies to specific allergens, including grass pollen, tree pollen, moulds, and others. Quantitative results are graded from Class 0 (not sensitised) to Class 6 (very high sensitivity).
Limitations:
Best for: Confirming suspected hay fever triggers when you cannot stop antihistamines; as a first-line investigation where skin prick testing is not available.
Molecular allergy testing — also called component-resolved diagnostics (CRD) — goes much further than standard tests. Instead of testing whole allergen extracts, it tests individual allergen proteins (components). This distinction matters enormously in hay fever.
Take grass pollen as an example. A standard test tells you whether you react to "grass pollen". A molecular test tells you which specific proteins within grass pollen are triggering your immune system — and whether they are genuine primary sensitisers, or cross-reactive proteins your immune system is confusing with something else.
Many people with grass pollen allergy also notice mouth tingling or itching when eating certain raw fruits and vegetables — apples, peaches, cherries, celery, carrots. This is oral allergy syndrome, caused by proteins in these foods that are structurally similar to pollen proteins. The immune system, primed to attack pollen, cross-reacts with the food. A standard test will show positive results for both the pollen and the food, making it look like you have multiple food allergies — when in fact you only have one primary allergy. Molecular testing can differentiate the two, preventing unnecessary dietary restrictions and clarifying your true allergy picture.
What it can tell you:
Limitations:
Best for: Moderate-to-severe hay fever; complex or year-round symptoms; suspected multiple allergies; anyone considering immunotherapy; unexplained oral allergy syndrome.
Not automatically. Allergy tests detect sensitisation — evidence that your immune system has been exposed to and produced antibodies against an allergen. But sensitisation and clinical allergy are not the same thing. Studies suggest that up to 30% of people who test positive to pollen allergens experience no symptoms at all.
This is why allergy test results should always be interpreted alongside your clinical history. A positive result means something if it correlates with your symptom pattern; without that context, it can be misleading. A GP or allergy specialist will always use the test result as one piece of evidence, not as a definitive diagnosis in itself.
If your symptoms are clearly seasonal (worse in spring and summer, better in winter), respond well to antihistamines, and don't significantly affect your quality of life, you may not need a formal allergy test at all. The pattern alone is usually enough to diagnose allergic rhinitis and guide treatment.
Testing becomes more valuable when:
We offer a comprehensive molecular allergy test — ALEX3 — which screens 300 allergens including 218 individual molecular components from a single blood draw. No antihistamine withdrawal required. Results reviewed with a GP in a follow-up appointment.
Antihistamines and nasal steroids manage symptoms — they do not alter the underlying allergic response. The only treatment that can do that is allergen immunotherapy (desensitisation), available as sublingual drops or tablets (SLIT) or injections (SCIT).
Immunotherapy gradually retrains the immune system to tolerate an allergen, reducing symptoms over time. It typically requires 3–5 years of treatment, but results can be long-lasting even after stopping. NICE has approved sublingual grass pollen immunotherapy for adults with allergic rhinitis where antihistamines and nasal steroids have not been sufficiently effective.
Crucially, to be a candidate for immunotherapy, you need a confirmed molecular allergy profile — knowing you react to "grass pollen" is not specific enough. You need to know which molecules within grass pollen you are sensitised to, to ensure the immunotherapy product matches your profile.
Molecular ALEX3 allergy test — 300 allergens, single blood draw, no antihistamine withdrawal. GP review included.
£295 all-inclusive
Book Now15 min result · must stop antihistamines · 40–60 allergens typically
No antihistamine stop · 1–2 days for results · limited panel
No antihistamine stop · 300 allergens · 218 molecular components · GP review