IgE blood test (immunoglobulin E)

Immunoglobulin E (IgE) is a class of antibodies that the immune system produces in response to allergens — dust, pollen, animal dander, food or medicines. When the body reacts “too much” to a substance that is essentially harmless, IgE attaches to that substance and activates cells that release histamine and other substances — and that is how the symptoms of an allergic reaction appear. A blood test can measure this in two ways: the total IgE (the whole amount of this class of antibodies in the blood) or specific IgE (the reaction to one particular, pre-selected allergen, nuts or cat hair for example). The specific IgE test is most often done as a panel — the reaction to several substances is checked at once. This test is used when a skin allergy test (a prick test) cannot be carried out because of a skin condition, because of medicines being taken, or because of a high risk of a severe reaction.

• When allergy symptoms appear: sneezing, a runny nose, itchy and watering eyes
• When urticaria (a rash), diarrhoea or vomiting appear after a particular food
• When there is shortness of breath, a cough or wheezing that may be linked to allergy
• When a skin allergy test (a prick test) cannot be carried out because of a skin condition, because of medicines being taken, or because of the risk of a severe reaction
• To establish which specific allergens the body is sensitive to (specific IgE)

Different laboratories use different reference limits for total and for specific IgE, so the exact interval is the one on your own laboratory result sheet. The MedlinePlus source this page relies on does not give specific numeric limits.

A raised IgE: what it can mean

A raised total IgE is most often considered a sign of allergy, while a raised specific IgE points to possible sensitivity to the particular allergen that was tested. Per MedlinePlus, IgE can also be raised for other reasons — smoking or a parasitic infection — so the result should be discussed with a doctor together with the symptoms.

• Allergy (a raised total IgE)
• Sensitivity to the particular allergen that was tested (a raised specific IgE)
• Smoking — can artificially raise the amount of IgE
• A parasitic infection — can give a false positive result

Symptoms that can go with a raised IgE

• A blocked or runny nose, sneezing
• Itchy, watering eyes
• Urticaria (a rash)
• Diarrhoea, vomiting
• Shortness of breath, a cough, wheezing

What is usually discussed with a doctor when the result is raised:

• Whether the result needs to be assessed together with the symptoms and the circumstances in which they appeared
• Whether a specific IgE panel is worth doing to establish particular allergens
• Whether smoking or a possible parasitic infection could have had an effect
• Further testing or treatment steps, if an allergy is confirmed

Related pages

• Eosinophils
• IgA
• IgG
• IgM
• CRP