Allergien richtig abtesten, einstufen und behandeln

The text was published in the online magazine Art & Science Krems, a co-operation project of KL.

Some have it, others don't. The symptoms can be anything from annoying to life-threatening. Some have a runny nose and burning eyes, others develop asthma or hives, and in the worst cases anaphylactic shock occurs, in which the airways constrict and swell up quickly. In an allergic reaction, the immune system mistakes harmless proteins for dangerous and triggers an overly strong defence. Thomas Eiwegger, Head of the Department of Paediatrics and Adolescent Medicine at St. Pölten University Hospital - a teaching and research location of KL - since 2021, sees all gradations of the diseases in clinical paediatric allergology.

In principle, every case is equally important to him, because uncertainty, worry and avoidance reactions are very stressful for families. More stressful than a careful diagnosis and a clear treatment plan: "All too often, a food allergy or asthma simply means that you can't go to this kindergarten, children's birthday party or school holiday," says the paediatrician, who is a specialist in allergy medicine Research groups at the Karl Landsteiner University in Krems and also works at the Research Institute of the Hospital for Sick Children at the University of Toronto. A great deal has been achieved in the diagnosis and treatment of food allergies.

Limits of knowledge

The bad news: "We don't know exactly why one child develops allergies and another does not. It is very likely that there is a combination of genetic risk factors and environmental factors, with the latter playing the greater role". There is a lot of evidence that diet and the microbiome, i.e. the entirety of microorganisms in the human body, their composition and diversity, play an important role: "It is not just which bacterial strains are present that is decisive, but what they do in the gut. This in turn depends on what we eat. Connections are repeatedly identified, but an enormous number of variables interact at the same time - so far we haven't been able to get our heads round this." The good news is that at a specialist centre such as St. Pölten University Hospital, it is possible to narrow down and clarify what a child is really allergic to and which treatment concept is appropriate.

Risk factors and recommendations

An overview of risk factors and recommendations can be found, for example, in the Allergy prevention guideline. Here are just a few examples. A confirmed risk factor for childhood asthma is smoking during pregnancy or around babies and small children. Not doing so is a difficult but feasible course to set. Growing up on a farm is associated with a lower risk of developing asthma and allergic diseases - not feasible or desirable for everyone. In families without an increased risk of allergies, keeping pets (cats or dogs) does not generally have to be restricted. This is grist to the mill for children who have been nagging their parents for a long time about wanting a pet.

Test + reaction = allergy

A positive test alone is not a diagnosis: "For an allergy to occur, a protein from the environment or food must suddenly no longer be tolerated and ignored by the immune system, but categorised as bad. Put simply, this sensitisation of the immune system occurs when allergens are presented to the immune system in the wrong context. In recent years, it has been discovered that the skin's barrier function plays a major role in this," says Eiwegger. Our gut digests food and signals to the immune system: everything is fine, this is food, just move on, no need for action, build up tolerance. In the case of neurodermatitis or atopic dermatitis in children (i.e. an antibody-mediated reaction to environmental allergens such as eczema), the children's barrier function is disturbed. Their skin is more permeable, so to speak, and an otherwise harmless bacterium can penetrate into skin layers where it does not belong. This leads to chronic inflammation because substances are introduced and agitated immune cells then also sound the alarm when it comes to food. Keeping everything away and avoiding it is a natural reaction, but not always a good strategy.

Successfully countering peanut allergy

But there are also success stories to tell. The clinical programme for treating severe food allergies at St. Pölten University Hospital is now the largest of its kind in Austria. From his work in Canada, Thomas Eiwegger knows that two to four per cent of children in the Anglo-American region have a peanut allergy, around one per class: "The recommendation to parents who have allergies themselves to actively avoid peanut-containing foods in their high-risk children has the opposite effect. We know that today. The children crawl around on the floor, where everything we eat is concentrated in the nanogram range, and that's where the allergen finds its way through the inflamed skin." If allergens are avoided, the natural mechanism of building up oral tolerance cannot take place.

In the LEAP study it was shown that the early and regular introduction of a peanut-based diet in countries with high peanut consumption can prevent the development of an allergy in high-risk patients (with atopic dermatitis and egg sensitisation) in more than 80 percent of cases. Other studies have shown that an early, diverse and age-appropriate introduction of complementary foods correlates with a lower rate of food allergies. And there is another piece of good news for all those in the middle. In the case of egg and milk allergies - an extremely restrictive combination - the allergy develops in over 80 per cent of children before they reach school age.

Diagnostics with a chip

At St. Pölten University Hospital, we work with controlled and dosed "provocations" with food - this is not something you try at home alone. "Our aim in treatment is to achieve freedom from asthma symptoms and precise diagnostics and early therapy using allergen-specific immunotherapy - we have high standards and many options". The third general recommendation would be to start immunotherapy at an early stage, because younger children respond better than when symptoms become entrenched. The test procedures have also developed considerably. In the allergy focal point hospital, a Chipmanufactured in Austria, 300 data points can be tested at once if it makes sense. Expertise is also available to correctly determine the result, possible cross-reactions and important molecular structures that are clinically relevant. Since 2024, allergologists have also been trained in St. Pölten and taught molecular biology skills. "Good tests help us to better understand which therapy makes sense, where there are good chances and where it is better to avoid the allergens," explains Thomas Eiwegger. It's easy to say, but it's not trivial. Mustard, for example, is a potent allergen that is not only deliberately placed next to barbecued food, but is also used in many ready-made products.

So-called "real" food allergies such as peanut, cashew or milk allergies are potentially life-threatening. However, cross-reactions such as those experienced by birch pollen allergy sufferers with fresh fruit and vegetables in a less severe form also severely restrict quality of life. The environment must be equipped and well informed about what is dangerous and what can be treated with an antihistamine. Therefore, good education, a good plan and a good risk assessment are also part of the treatment. Research into suitable therapies is continuing, for example at Karl Landsteiner Private University and at the Danube Allergy Research Cluster. In order to communicate allergies in an age-appropriate way, an interactive children's book has just been published.

Incidentally, the author was a paediatrician and early immunologist working in Vienna, Clemens von Pirquetwho coined the medical term "allergy" in 1906. The physician recognised that antibodies produced by the immune system not only mediate protective immune responses, but can also trigger diseases. The word is derived from the Greek (allos = other, ergon = labour). Thomas Eiwegger considers Clemens von Pirquet to be an "incredibly important person" and is, so to speak, continuing his pioneering work and path.

Text: Astrid Kuffner

The Online magazine ask - art & science krems provides insights into the lively cultural and research city of Krems. It raises awareness of the intellectual, scientific and artistic charisma of this place and thus anchors it more firmly in the consciousness of exponents and those interested in art and science. In addition, ask seeks out interfaces between the institutions that may not be obvious at first glance.

KL is a co-operation partner of the magazine and has contributed ideas for stories and portraits since the beginning.