Immunoglobulin E

Immunoglobulin E (IgE) is an antibody your immune system produces primarily in response to allergens and parasitic infections. Although it circulates in very small amounts compared to other antibodies, IgE punches well above its weight, it is the driving force behind allergic reactions, from hay fever and eczema to food allergies and allergic asthma. When your body encounters something it considers a threat (such as pollen, pet dander, dust mites, or certain foods), IgE binds to immune cells called mast cells and basophils. On re-exposure, these IgE-coated cells release histamine and other chemicals, producing the familiar symptoms of allergy, itching, sneezing, swelling, or in severe cases, anaphylaxis.

A total IgE test measures the overall level of IgE antibodies in your blood. It does not tell you what you are allergic to, that requires specific IgE testing for individual allergens. However, a raised total IgE can be a helpful screening tool that suggests your immune system has an allergic tendency (sometimes called atopy). Moderately elevated IgE is common in people with eczema, asthma, hay fever, or food allergies. Very high levels can occasionally be seen with parasitic infections (particularly in travellers), certain immune conditions, or, rarely, more complex immune disorders.

Normal IgE does not completely rule out allergies, some people with genuine allergic conditions have IgE levels within the standard range. Similarly, mildly raised IgE does not always mean you will experience allergic symptoms. If your IgE is outside the expected range, your GP can help determine whether allergy testing, lifestyle adjustments, or specialist referral would be appropriate.