Quick answer
What is an allergy blood test?
An allergy blood test is a blood test that measures specific IgE antibodies to particular allergens, supporting an allergy diagnosis alongside your symptom history. A positive result confirms sensitisation but does not always mean a clinical allergy. Skin prick tests are often used too, so results are best interpreted with an allergy specialist.
What a specific IgE allergy blood test measures
A specific IgE allergy blood test measures the antibodies your immune system makes when it becomes sensitised to an allergen. It forms part of a wider diagnostic workup rather than a standalone test, so the result is always considered together with your symptoms and history.
When an allergy blood test is used
An allergy blood test may be used if you have a history of anaphylaxis, if your triggers are unclear, or when immunotherapy is being considered. It is not used to investigate non-allergic food intolerance, which needs a different approach.
How allergy blood test results are interpreted
Your clinical history is the most important factor when interpreting the results, because sensitisation alone does not confirm an allergy. In some cases, component testing is used to refine the assessment of risk for particular allergens.
How allergies are managed after diagnosis
Once an allergy is confirmed, management usually centres on avoiding the trigger, and adrenaline auto-injectors are prescribed for people at risk of anaphylaxis. Allergen immunotherapy may be offered in selected cases under specialist care.
Common questions about the allergy blood test
- What is the difference between an allergy blood test and a skin prick test?
- Both tests detect allergic sensitisation, but they suit different situations. A skin prick test gives faster results in the clinic, while a blood test is preferred if you are taking antihistamines or have a skin condition that could affect the results.
- Does a positive allergy blood test mean I am allergic?
- Not necessarily; a positive result confirms sensitisation, but its clinical relevance depends on your symptom history. Some people can eat a food safely despite testing positive, which is why the result is interpreted alongside what actually happens to you.
- Can allergy blood tests diagnose food intolerance?
- No; IgG food panels are not validated and are not used by the NHS to diagnose intolerance. It is best to avoid commercial unproven tests, which can lead to unnecessary food restriction.
- How is allergy tested in children?
- Children with suspected allergy usually need a specialist assessment. Milk and egg allergies are common in early childhood, and many children outgrow them over time.