Total IgE (Immunoglobulin E)

What is Total IgE?

Immunoglobulin E (IgE) is one of the classes of antibodies produced by the immune system, and it is normally present in the blood in very small amounts. In people with allergies, large amounts of IgE are produced against substances that are actually harmless, such as pollen, house dust mites or certain foods. These antibodies bind to mast cells and, when the allergen is encountered, trigger allergy symptoms by causing the release of substances such as histamine. In some people this reaction stays limited to mild symptoms such as sneezing and itching, while in others it can lead to more severe reactions.

IgE also plays a role in the defense against certain parasites. The Total IgE test measures the total amount of IgE in the blood using an immunological method, regardless of which substance it is directed against. It therefore gives a general idea of allergy tendency but does not show what the person is allergic to. The IgE level in the blood increases with age throughout childhood.

When is the Total IgE test ordered?

Total IgE is most often ordered in people with symptoms of allergic disease to assess whether the picture is related to allergy. A high level of cells called eosinophils in a blood count is another reason for ordering the test. It is also used in planning certain asthma treatments and in investigating rare immune system diseases. Especially in people with more than one allergic disease, such as eczema and asthma, it can help in understanding the extent of the allergic predisposition.

• Allergic rhinitis symptoms such as sneezing, runny nose and itching
• Asthma or recurrent wheezing
• Eczema (atopic dermatitis) and long-lasting itching
• Suspected food allergy
• Suspected parasitic infection and high eosinophils

How do you prepare for the Total IgE test?

No fasting is required for Total IgE, and blood can be given at any time of day. Although allergy medicines such as antihistamines can affect skin tests, they usually do not affect the measurement of total IgE in the blood; for this reason, you do not need to stop your medicines unless your doctor tells you to. If you are receiving a biologic treatment for allergy or asthma, be sure to mention it, because these treatments can change the result.

Because high-dose biotin supplements can affect the measurement with some immunological methods, tell your doctor if you take them. Telling your doctor about a recent infection or a trip abroad can provide clues when assessing the possibility of parasites. The test is run on a small amount of blood taken from the arm, and the sample can be taken by a nurse at your home or workplace.

What does the Total IgE result mean?

A high total IgE most often suggests an allergic predisposition (atopy) and can occur together with diseases such as allergic rhinitis, asthma or eczema. Parasitic infections, smoking, certain fungal lung diseases and rare immune system disorders can also raise the value. An elevated level alone does not point to a specific allergy; specific IgE or skin tests may be needed to find out which substance you are sensitized to.

A normal or low result does not definitively rule out allergy; some people can be allergic to a particular substance while their total IgE is normal. Low values often have no significance on their own. Because IgE levels change with age during childhood, reference ranges can differ by age, as well as by laboratory and sex; you can see the laboratory's own range on this page. Your doctor should decide what your result means, together with your complaints and other tests.