Immunoglobulin E – what the IgE value means

Immunoglobulin E – what the IgE value means

Immunoglobulin E (IgE) is an antibody that plays a vital role in developing allergies and the defence against parasites. The amount of IgE in the body can be increased in allergies. Therefore, if an allergy is suspected, an IgE test is carried out to determine the IgE level in the blood. But when is the IgE value too high? What are the most common causes of increased IgE levels, and how can IgE levels be lowered? You can find out more about this here.

What is immunoglobulin E?

Immunoglobulins are proteins and components of the body’s defence system, the immune system. Immunoglobulins are also called antibodies. The immune system forms antibodies in response to foreign substances, so-called antigens. They are designed to fight pathogens and harmful foreign substances that enter the body.

There are many different antibodies divided into classes. One of these classes is immunoglobulin E, also known as IgE. Each class of antibodies has its function in the immune system. IgE is particularly important in allergic reactions and the defence against parasites.


Other immunoglobulins

Other immunoglobulins play a central role in the human immune system :

  • Immunoglobulin A (IgA) is mainly found in bodily secretions such as tears, saliva, nasal mucus and breast milk. It binds pathogens and triggers inflammatory reactions.
  • Immunoglobulin M (IgM)  is found in the blood and is formed upon first contact with a specific pathogen. This process is called the primary immune response.
  • Immunoglobulin G (IgG) is a so-called secondary antibody and forms the central part of the antibodies in the blood. It is formed upon repeated contact with a specific pathogen. IgG causes the scavenger cells (macrophages) to destroy the pathogen. This is known as a secondary immune response.

How does an allergy develop?

In an allergic reaction, the immune system reacts to actually harmless antigens in the environment. The antigens that trigger allergies are also referred to as allergens. Possible allergens include:


What role does IgE play in allergic reactions?

With specific allergic reactions of the so-called immediate type (type I), a reaction occurs within a few seconds to minutes after contact with the allergen. IgE drives the allergy-related inflammatory process and is responsible for this rapid reaction. IgE causes the release of the messenger histamine, which can lead to typical symptoms such as swelling, itching and redness.

In addition to the immediate type, there are also allergies of type II (cytotoxic type), type III (immune complex type) and type IV (delayed type). Two immunologists developed the division into these four allergy types in the early 1960s, and it is still valid today.

What is an IgE test?

In some instances, a doctor can carry out an IgE test. This is a blood test in which a blood count is taken, and the IgE value determines the blood values. An IgE test can be helpful for two reasons:

  1. Since there is a specific IgE type for each antigen, examining the IgE types can be used to determine which antigen has led to an allergic reaction. For this purpose, an allergy test, more precisely an antigen-specific IgE antibody test, is carried out.
  2. The total IgE value determines the total IgE amount in the blood. The total IgE value can increase due to a parasite infestation or an allergic reaction and is rarely too low.

IgE allergy test – which immunoglobulin E type is present?

The allergen-specific IgE antibodies can be determined using an IgE test to clarify which allergens have led to a specific allergic reaction. With the help of this blood test, the exact type of allergy (e.g. grass pollen allergy, mould allergy, house dust mite allergy and others) can be determined. In this way, allergy-causing substances can be avoided in the future, or appropriate allergy treatment can be initiated.


How the IgE test works

The IgE test uses a small amount of the person’s blood. Both the immunoglobulin E types and the total amount of IgE (total IgE value) are determined in the blood sample.

Depending on the level of the total concentration of IgE in the blood, it is divided into different classes. The lowest class (class 0) indicates no allergy, and the highest class (class 6) indicates severe allergies.

What is an average IgE value?

The amount of total IgE depends on age. Children show a much lower value than adults. The value increases in the first years of life and is maintained later, in adulthood. The IgE value is measured in IU/ml, International Units per millilitre of blood serum, or in µg/l, which means micrograms per litre of blood serum.

The IgE values ​​(total IgE) shown in the following table are considered normal, although the average values ​​may vary slightly depending on the laboratory:

IgE values ​​in an allergy test

An allergy test not only determines the IgE type, which indicates a specific allergen but also allows conclusions to be drawn about what you are allergic to. In addition, the amount of allergen-specific IgE antibodies is also measured. It provides information about how severe an allergy to a specific allergen can be.

For this purpose, a blood sample is examined using a particular laboratory test. The so-called radio-allergo-sorbent test, or RAST for short,  is a method that can be used to determine and classify the amount of allergen-specific IgE antibodies. An alternative is the CAP (carrier polymer system test), which is more modern but delivers comparable results to the RAS test. There are a total of six so-called RAST classes or CAP classes.

The results of the RAST alone do not provide information on whether an allergy is present. To detect or rule out an allergy, the anamnesis (conversation with the patient) and the results of other tests, such as a skin test and the so-called prick test, must always be considered and evaluated.

Deviations from the above reference values ​​do not necessarily indicate health problems. It is, therefore, advisable to always discuss the individual blood values ​​with the doctor treating you.


Immunoglobulin E increased – what are the causes?

If the total IgE value is increased, i.e. the total amount of immunoglobulin E in the blood, this can indicate a type I allergic disease or a parasite infestation. Concrete possible causes are, for example:

 The total IgE value is also often elevated in certain forms of neurodermatitis and hives . In addition, a high level of IgE can also be a sign of the rare hyper-IgE syndrome (HIES), an inherited chronic disease in which the immune system is affected. However, this disease only occurs in around 1 in 100,000 people.

Treatment: what to do with elevated immunoglobulin E?

The original task of immunoglobulin E, as part of the immune system, is to recognize and eliminate foreign substances in the body. To perform this task, IgE increases when allergens are detected. The result is a high IgE value.

However, this increase in IgE is only sometimes desired, for example, in the case of an allergy. The IgE value and, thus, the allergic reaction can be reduced in different ways:

  1. Avoid known allergens: If no allergenic substances are present, the allergic inflammatory process is slowed because less IgE is released.
  2. Getting the body used to the allergens: This is what is known as hyposensitization. The allergens are regularly injected under the skin in increasing doses or administered orally. The latter is called sublingual immunotherapy.
  3. Neutralize IgE with an antibody against IgE: This treatment is also known as anti-IgE and is only given in some instances.

Important: The level of the IgE value is not directly related to the severity of the allergy or a parasite infestation. Allergy symptoms can also be present, but the IgE value is not significantly increased. The IgE value can also be increased, but there is no allergy. In this case, the increased IgE value can also have other causes, as already described.

IgE value too low: What is behind it?

IgE levels that are too low are usually acceptable. Only in sporadic cases are congenital immune defects, Louis-Bar syndrome (ataxia telangiectasia), diseases of the bone marrow or kidney diseases (nephrotic syndrome) the reason for a low IgE value.


Anti-IgE – what is it?

Anti-IgE is an antibody against immunoglobulin E. The artificially produced anti-IgE antibody omalizumab is currently used as an add-on therapy in severe allergic asthma and urticaria to suppress the IgE-mediated allergic reaction and, thus, the symptoms. Omalizumab attaches itself to the IgE antibodies and thus prevents the allergic inflammatory process from taking place.

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