Who doesn't know the typical Christmas smell of spices, mulled wine and winter? Nuts are a standard ingredient in Christmas biscuits. Whether gingerbread, biscuits or stollen: Allergy sufferers can't just eat them.
Nuts are becoming increasingly popular as a snack or in international dishes. At the same time, nut allergies are on the rise. Nuts are foods that come from very different botanical families. They contain different allergen components, some of which can cause severe systemic reactions and others more mild allergic symptoms due to cross-reactivity, such as in pollen-associated nut allergy.
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Doctors distinguish between two types of nut allergies:
Primary nut allergy: This form already occurs in childhood and is often triggered by peanuts. The cause: The body mistakenly perceives certain proteins of the nuts as the enemy and reacts with symptoms. These actually harmless proteins are called allergens. Often these allergies develop during childhood and remain throughout life. This has an impact on quality of life, as even traces of nuts can cause severe reactions. Symptoms include nausea, vomiting, diarrhoea but the likelihood of a severe allergic reaction or anaphylactic shock is greater with this type. Peanuts and hazelnuts in particular increase the risk. The bronchial tubes constrict and trigger symptoms such as coughing and shortness of breath. Blood pressure drops and the heart beats irregularly. In extreme cases, a nut allergy can lead to cardiovascular or respiratory arrest.
Secondary nut allergy: Doctors also call this form a cross allergy, it mostly occurs in adults. Doctors speak of a cross-reaction when a person first reacts to a certain allergen and then to another allergen that is similar to the first. In pollen-associated nut allergy, the triggers are often early-flowering plants such as birch, hazel, or oak. This type of allergy often affects hazelnuts. Food allergy sufferers in particular should be very careful, as even traces of nuts can trigger severe symptoms. An allergic reaction to nuts can cause different symptoms, but cross-reactive nut allergies tend to be milder. An oral allergy syndrome accompanied by tingling, swelling, numbness or itching in the face or mouth area, skin rash or mild digestive symptoms have been described.
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Diagnosis
In order to make a diagnosis of nut allergy, the doctor usually arranges a series of tests after an extensive anamnesis interview. In a so-called prick test or skin test, he or she applies the nut allergens in the form of droplets to the upper arm. If the skin reddens or wheals form, this is an indication of a nut allergy. In addition, a blood test is carried out to detect specific IgE antibodies in the blood. A very accurate, quick and easy test is the ALEX2 Allergy Explorer. In order to find out to which nuts a sensitisation exists, for risk assessment, differentiation of a real nut allergy from cross-reactivities, it is useful to establish a comprehensive sensitisation profile. The specific IgE determinations with the comprehensive allergen panel on the ALEX2 allergy test allows to distinguish a "true" nut allergy from cross-reactions and provides extensive information about the risk of developing serious reactions when exposed to nuts. Often, specific IgE antibodies to the storage proteins such as albumins and globulins indicate a "true" peanut allergy and an increased risk of severe reactions. Storage proteins are stable to heat and digestion, so allergy sufferers are also at risk with roasted/heated preparations.
Examples:
- Peanut: Ara h 1, Ara h 2, Ara h 3, Ara h 6
- Brazil nut: Ber e 1
- Cashew: Ana o 2, Ana o 3
- Hazelnut: Cor a 9, Cor a 11, Cor a 14
- Macadamia: Mac i
- Pistachio: Pis v 1, Pis v 2, Pis v 3
- Soy: Gly m 5, Gly m 6, Gly m 8
- Walnut: Jug r 1, Jug r 2, Jug r 4, Jug r 6
In contrast, PR-10 proteins of hazelnut (Cor a 1), peanut (Ara h 8) and soy (Gly m 4) are associated with local symptoms such as oral allergy syndrome (OAS) and are markers for birch pollen-associated cross-reactions. These proteins are labile to heat and digestion, so a roasted/heated preparation is usually tolerated.
Lipid transfer proteins (nsLTPs) of hazelnut (Cor a 8), peanut (Ara h 9) as well as walnut (Jug r 3) are frequently associated with severe reactions in addition to oral allergy syndrome LTPs are stable against heat and digestion and are marker allergens for cross-reactivities to other food LTPs.
Therapy options
The common therapy for nut allergies is to avoid allergen contact and take antihistamines for milder symptoms. Severe allergic reactions, including anaphylactic shock, are known to occur, especially with peanut allergy. Therefore, the patient and his/her environment must always be well trained in the use of emergency measures and emergency medication. Researchers are working on an oral immunotherapy that may be able to cure peanut allergies in the future. The development of epicutaneous immunotherapy for peanut allergy is now well advanced (testing in phase III trials). Therefore, approval of certain therapy products for peanut allergy is possible in the foreseeable future.