Updated: Mar 28
Allergy blood tests, along with skin tests, are used to diagnose allergies. Blood tests are becoming increasingly popular due to the possibility of testing a large number of allergens.
In the diagnosis of allergies, the general blood test determines the total level of immunoglobulin class E (IgE) antibodies in the blood, which increase as a result of sensitisation to an allergen. IgE tests for a specific allergen are then performed, usually in the form of allergy panels, e.g., testing for food allergens, pollens and others.
In order to choose the right way to diagnose the allergy, it is necessary to collect the necessary information about the symptoms. Because there are many allergens, determining the circumstances of the onset of symptoms is important (for example, frequent sneezing in the presence of a pet or abdominal pain after eating).
Steps for diagnosis with blood tests
Blood tests for allergy (so-called serological tests) are divided into two stages:
General IgE test – measures the total amount of immunoglobulin E in the blood
Specific IgE test – measures immunoglobulin E in the blood in response to specific allergens individually or in panels
The advantage of blood tests is that the person does not have to come into contact with the allergen that is potentially dangerous for them. An allergy blood test is also safer to detect a suspected allergy in children. However, it should be noted that the amount of IgE antibodies in the blood is also related to age, which is why blood tests are not usually recommended for children under five years of age.
General IgE test
During an allergic reaction, IgE antibodies are formed in the body. Allergens entering the body, such as nuts or pollen, trigger the production of these antibodies. A high level of IgE antibodies in the blood indicates an allergic process when its concentration exceeds 100 IU/ml. The general IgE test can be done in a medical laboratory or with a rapid at-home allergy test.
Specific IgE test
If the general test shows that the level of IgE antibodies is too high (above 100 IU/ml), the search for the exact cause of the allergic reaction can begin. Each allergen triggers the production of specific IgE antibodies. These, in turn, make it possible to determine which allergen or group of allergens are responsible for the onset of symptoms.
Depending on the method of absorption, we observe different allergy symptoms - this is a very valuable guide when choosing a test panel. If you experience bloating, abdominal pain or diarrhoea after eating, you should be tested for food allergens.
A single allergen or so-called allergy panels can be determined in the laboratory. Panels allow multiple allergens to be tested at once.
Food allergens - these include allergens contained in food. This is one of the most common types of sensitisations. The panel includes allergies caused by nuts, fruits, dairy products, soy, seafood and more.
Inhalant allergens - these include allergens penetrating through the respiratory tract. The panel includes sensitisation caused by pollens from trees, flowers and grasses, epidermis of animals - cats, dogs, horses, fungi (e.g., Aspergillus fumigatus) and other.
What is the difference between a blood and skin allergy test?
Allergy blood test and skin test are the two main testing methods when an allergy needs to be established. In allergy skin tests, the specialist makes small pricks or scratches on the skin and then applies allergens to check the reaction.
But some people can't get a skin test. If someone is being treated for hives and is taking antihistamines, the skin test will not give a reliable result. With the blood test, it can be immediately established whether the symptoms are caused by an allergy or not, and therefore the next step can quickly be taken. Blood tests do not require contact with the allergen, which may be dangerous to humans. Blood tests are also better for children because they don't require multiple epidermal punctures.
How do you prepare for the blood test?
Fortunately, you don't need to do anything special to prepare for this type of examination. The test does not require fasting beforehand and you do not need to stop antihistamines, which are very often used to relieve allergy symptoms. You can test yourself from the comfort of your own home with a quick at-home allergy test ALLERGY-Check and if high levels of IgE are found look for the specific allergen responsible for the allergic reaction.