What happens during an allergic reaction, how can it be detected, and why should it be monitored?

Allergies affect at least 30% of the population, and their prevalence is increasing worldwide. They can have a significant impact on everyday life—from unpleasant symptoms such as a runny nose, itching, or eczema, to limitations in daily activities and even severe allergic reactions. However, there is still insufficient information about the specific allergens to which the Czech population is sensitized. This is why it is important to monitor allergies in population studies and investigate which factors influence their development and whether they may also be associated with other diseases.

What happens in our body during an allergic reaction

An allergy develops when the immune system overreacts to substances that are harmless to most people. Some of the most common allergens include pollen, dust mites, animal dander, foods, and moulds.

When a susceptible person comes into contact with an allergen, sensitization may occur. During this process, the body produces specific antibodies called immunoglobulin E (IgE), which bind to immune cells (mast cells or basophils). At this stage, no symptoms are present.

When the same allergen enters the body again, it binds to IgE on the surface of mast cells or basophils, causing these cells to release specific chemical substances, such as histamine. These substances trigger an inflammatory response, which can cause symptoms such as a runny nose, itching, eczema, or swelling.

As part of our population studies, we measure sensitization to individual allergens, i.e. the presence and levels of specific IgE antibodies in the blood. For this purpose, we use the ALEX test, performed on the MAD MAX analyzer machine. Compared with conventional skin prick tests, this method allows us to test for antibodies against 295 allergens simultaneously (including, for example, pollen, dust mites, moulds, animal allergens, and foods), using only a small amount of blood serum (200 microlitres).

The test also makes it possible to determine sensitization not only to allergen extracts (mixtures of different molecules), but also to individual allergen molecules. This is particularly important in the case of cross-reactivity. Some molecules from different sources can be so similar that they are recognized by the same IgE antibodies. For example, a person sensitized to pollen may also experience symptoms after eating certain types of fruit or vegetables.

The test uses an ELISA-based method with nanoparticle microarray technology, in which individual allergens are immobilized on the test surface. Specific IgE antibodies from the blood serum bind to these allergens and are subsequently detected through an enzymatic reaction that produces a coloured signal. Sensitization to an allergen can therefore only be detected if the person has previously been exposed to that allergen and has developed IgE antibodies against it.

Specific IgE antibodies from the blood serum bind to these allergens and are subsequently detected through an enzymatic reaction that produces a coloured signal. Sensitization to an allergen can therefore only be detected if the person has previously been exposed to that allergen and has developed IgE antibodies against it.

In general, the higher the level of specific IgE antibodies, the greater the degree of sensitization to the particular allergen. However, a positive result does not necessarily mean that the allergen actually causes an allergic reaction and must be interpreted in the context of the individual and their symptoms. We only refer to an allergy when exposure to a particular allergen is accompanied by corresponding clinical symptoms.

It is also important to note that allergy is not a fixed condition—its symptoms and severity can change throughout a person's life.

Testing for allergen sensitization is carried out as part of our studies for research purposes only and not for diagnostic purposes. In the event of a positive result, we recommend that participants discuss the findings with their general practitioner or an allergist.

What is our Young Adults cohort allergic to?

The graphs below show how many of the 1,054 participants in the Young Adults study reported in questionnaires that they had been diagnosed by a doctor with an allergy to pollen, food, or insect stings, or with asthma, which can be triggered by allergies.