IgE (Immunoglobulin E) Blood Test

Allergy blood tests frequently give false-positive results, indicating an allergy when there isn’t one. IgE blood tests don’t indicate the severity of an allergy, though the higher your result, the more likely you are to react to an allergen. This test can’t pinpoint specific allergens – it’s important to keep a diary of potential allergens you’ve been exposed to before your symptoms came on.

False-negative results are also possible, where the test indicates no allergy despite there being one. This is less common than a false-positive result but can still occur. This is usually due to test timing (for example, taking the test a long time after allergy symptoms have settled), the type of allergy (delayed hypersensitivity reactions and non-IgE-mediated allergies like food intolerances are often not picked up by this test), or if baseline IgE levels are very low to start with.

A negative result does not completely rule out an allergy, particularly if there has been no recent exposure to the suspected trigger. If an allergy is still strongly suspected, you should discuss the result with your doctor, who may recommend further testing, such as skin prick testing.

Decisions about reintroducing foods, especially where there is a history of severe allergic reactions or anaphylaxis, should always be made in consultation with a GP or allergy specialist, who can assess your full clinical history.