Allergy Testing in London. Find Out What You Are Reacting To

Last updated June 2026

Medically reviewed by the GMC-registered doctors at The Online GP by The Wellness

Living around an allergy you cannot name means guessing, avoiding the wrong foods, and never quite feeling in control. Proper allergy testing replaces that guesswork with answers. This guide explains the difference between skin prick and blood testing, which one suits which problem, and how to get tested properly in London, with a doctor who turns the result into a plan rather than a printout.

Want to know exactly what you are allergic to. Message The Online GP by The Wellness on WhatsApp or email team@thewellnesslondon.com.

What types of allergy testing are there

The two main methods are skin prick testing and IgE blood testing. Skin prick testing applies small amounts of allergen to the skin and reads the reaction within about 15 to 20 minutes, giving same-visit results. Blood testing measures allergen-specific IgE antibodies and can screen for many allergens at once, with results in a few days.

Each method has its strengths. Skin prick testing is often called the most reliable method for immediate-type reactions, such as those to pollen, pet dander, dust mites and certain foods, and it gives an answer during the appointment. IgE blood testing is useful when you cannot stop antihistamines, when skin testing is impractical, or when you want a broad screen, with modern panels checking for up to around 300 allergens from one sample. Patch testing is a separate test for delayed skin reactions. A doctor chooses the right test, or combination, based on your symptoms, because the wrong test can give a misleading answer.

Which allergy test do I need

The right allergy test depends on your symptoms and history. Immediate reactions such as hives, swelling or breathing changes after a food or exposure usually point to skin prick or IgE testing. Persistent skin rashes from contact may need patch testing. A doctor matches the test to the problem rather than running everything.

This matters because allergy testing is easy to get wrong by over-testing. A long panel run without clinical direction can flag sensitivities that are not causing your symptoms, leading to needless food avoidance and anxiety. The useful approach is to start from your story, what happens, how quickly, and to what, and then test for the likely culprits. A doctor at The Online GP by The Wellness takes that history first, selects the appropriate test, and interprets the result in context. That is the difference between a result you can act on and a list of numbers that confuses more than it clarifies.

For the right test, not every test, enquire on WhatsApp here.

How does The Online GP by The Wellness approach allergy testing

The Online GP by The Wellness is the go-to first point of contact for allergy testing, providing doctor-led assessment, blood-based IgE testing in house, and connection to consultant immunology partners for skin prick testing, food challenges and immunotherapy when these are the right step. You get a clear diagnosis and a management plan, not just a result.

The pathway is built around interpretation and next steps. A GMC-registered doctor takes a detailed history, arranges the appropriate test, and explains what your results mean for daily life. Where specialist allergy care is needed, such as supervised skin prick testing, an oral food challenge, or immunotherapy for conditions like severe hay fever, the team connects you with trusted consultant immunologists and coordinates your care. A management plan typically covers allergen avoidance, the right medication, and, where appropriate, an adrenaline auto-injector and a clear emergency plan. If you have ever had a severe reaction, this planning is the most important part of the whole process.

What is a management plan and why does it matter

A management plan is the practical output of allergy testing, a clear set of instructions on what to avoid, which medication to use, and what to do in an emergency. A test result without a plan is only half the job, and the plan is what actually keeps you safe and comfortable day to day.

For most people, a good plan means knowing their triggers, having the right antihistamine or nasal treatment, and understanding how to reduce exposure. For people at risk of severe reactions, it means carrying an adrenaline auto-injector, knowing exactly how and when to use it, and having an emergency plan that family or colleagues understand. Where treatment can reduce the allergy itself, immunotherapy may be an option discussed with a specialist. The Online GP by The Wellness makes sure you leave with the plan, not just the diagnosis, and stays your point of contact if your needs change.

For testing plus a plan you can rely on, message us on WhatsApp.

How to prepare for an allergy test

Preparation depends on the test. For skin prick testing you usually need to stop antihistamines for two to three days beforehand, as they can suppress the reaction and give a false result. Blood testing has no such restriction, so it is the better option if you cannot pause your medication. Continue asthma inhalers and other regular medicines as normal.

The team will tell you exactly how to prepare when you book, but the antihistamine rule is the one people most often miss. Taking cetirizine, loratadine or fexofenadine in the days before a skin prick test can mask a genuine allergy, which is why the test is either rescheduled or replaced with a blood test in that situation. Knowing this in advance saves a wasted appointment. For anything else, a doctor will guide you, including which allergens to focus on based on your history.

Frequently asked questions

What is the difference between skin prick and blood allergy testing

Skin prick testing applies allergens to the skin and reads the reaction within about 15 to 20 minutes, giving same-visit results. Blood testing measures allergen-specific IgE antibodies, can screen for many allergens at once, and does not require stopping antihistamines, with results in a few days.

Do I need to stop antihistamines before allergy testing

Yes for skin prick testing, usually for two to three days, as antihistamines can mask a genuine reaction. Blood testing does not require this. Continue asthma inhalers and other regular medicines, and your doctor will advise when you book.

Can allergy testing diagnose food allergies

Yes, skin prick and IgE blood testing help identify food allergies, and where there is uncertainty a supervised oral food challenge with a specialist can confirm a diagnosis. A doctor interprets results in the context of your symptoms.

Will I get a treatment plan

Yes. The Online GP by The Wellness provides a clear management plan covering avoidance, medication and, where needed, an emergency plan and adrenaline auto-injector, plus referral to consultant immunology for immunotherapy when appropriate.

How do I book allergy testing

Send a WhatsApp message and a GMC-registered doctor will arrange the right test, usually within the same week, with results and a plan explained clearly.

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