IgE (immunoglobulin E)

Total IgE (immunoglobulin E) shows the amount of class E antibodies in blood, which mediate allergic reactions and defence against parasites. The test gives a general picture of allergic tendency but does not identify what someone is allergic to: specific IgE antibodies to individual allergens serve that purpose.

Who the test is for

• people with suspected allergic disease, such as allergic rhinitis, allergic asthma or atopic dermatitis;
• people with suspected parasitic infection, alongside a blood count showing raised eosinophils and stool examination for cysts and parasites;
• people with asthma or cystic fibrosis and suspected allergic reaction to Aspergillus mould (allergic bronchopulmonary aspergillosis);
• people undergoing investigation of rare immune disorders, such as hyper-IgE or Wiskott–Aldrich syndrome;
• people with severe allergic asthma before starting certain biological medicines, when the dose depends on total IgE.

What IgE is and what it shows

IgE is the least abundant antibody class in blood. In people prone to allergies, the immune system produces IgE against normally harmless substances, such as pollen, dust mites, animal hair or food. These antibodies bind to mast cells and basophils, which release histamine and other substances on re-exposure to the allergen. The consequences are sneezing, a runny nose, itching, hives or difficulty breathing, and in the most severe form anaphylaxis.

IgE also helps defend against intestinal parasites, so it rises in some parasitic infections.

Total and specific IgE

Total IgE is the sum of all IgE antibodies in blood. It is raised in many people with allergies but also in parasitic infections, smokers and some other conditions, so it does not establish allergy on its own. Normal total IgE does not rule out allergy: some people with a clear allergy have total IgE within the reference interval.

Specific IgE measures antibodies to a precisely defined allergen. A positive result means sensitisation: the body has produced antibodies to that allergen. Sensitisation is not always the same as allergy: allergy means the result matches symptoms occurring on exposure to that allergen. Testing options are described in the article on allergy tests.

Preparation and sample

Total IgE is measured in venous blood and fasting is unnecessary. Antihistamines do not affect blood IgE measurement, so they do not usually need to be stopped for this test, unlike skin tests. Do not stop prescribed medicines without agreement with your doctor.

How to interpret the result

IgE is expressed in kIU/L (equivalent to IU/mL). The reference interval depends strongly on age because IgE changes during childhood; the range for your age and the method is printed on the report. A doctor interprets results alongside symptoms and, if necessary, specific IgE.

• Raised total IgE most often accompanies atopic diseases: atopic dermatitis, allergic asthma and allergic rhinitis. It may also be raised in parasitic infections, allergic bronchopulmonary aspergillosis, smokers and some rare immune diseases. Very high levels are often found in severe atopic dermatitis.
• Normal or low total IgE does not rule out allergy to an individual allergen. If symptoms suggest allergy, a doctor requests specific IgE or skin tests.

How to arrange testing

You can have blood taken without an appointment or referral at one of our branches across Croatia (listed under Contact). Prices for all tests and panels are available in the service price list. If you want to know which allergens you are sensitive to, a more suitable option is ALERGO 295, a test for specific IgE antibodies to 295 food and environmental allergens, including egg, milk, wheat and peanut, from one blood sample. It also includes total IgE and can be performed from the earliest age. With ALERGO 295 labelled “+ interpretation”, result interpretation is provided as part of a free consultation.

Frequently asked questions

What does raised blood IgE mean?

Most often a tendency to allergic disease, but raised IgE can have other causes, such as parasitic infection or smoking. The result does not show which allergen you react to, so a doctor decides whether to test specific IgE based on symptoms.

Can my IgE be normal even if I have an allergy?

Yes. Total IgE is the sum of all IgE antibodies, and antibodies to one allergen may be present even when the total level is normal. With clear symptoms, such as seasonal sneezing or a reaction to a particular food, measuring specific IgE is more useful.

Should I stop taking antihistamines before blood collection?

Generally not for blood IgE measurement, because antihistamines do not affect antibody levels. They need to be stopped before skin tests, according to a doctor’s instructions.

Is an IgE test the same as a food intolerance test?

No. IgE antibodies mediate allergic reactions, while the food intolerance test measures IgG antibodies to foods. IgG antibodies to foods eaten regularly are common in people without symptoms too, so the European Academy of Allergy and Clinical Immunology (EAACI) does not recommend IgG testing to diagnose allergy or intolerance. If you suspect food allergy, discuss specific IgE testing with a doctor.