Cross-allergies affect millions of people – often without their knowledge. For example, someone who is allergic to birch pollen may suddenly also be sensitive to apples, nuts, or carrots. But what exactly is behind this phenomenon? How can cross-allergies be recognized, treated, and avoided in everyday life? In this comprehensive article, you'll learn everything you need to know about cross-allergies – explained scientifically and in an easy-to-understand manner.
What is a cross-allergy?
A cross-allergy occurs when the immune system overreacts to similar protein structures in different allergy-causing substances (allergens). This means that someone who already has a pollen allergy (hay fever) can also react allergically to certain foods or other substances, even if they previously tolerated them well.
These cross-reactions occur because the molecular structures of the allergens are similar – the immune system confuses them and raises the alarm.
Cross allergies vs. primary allergies – what is the difference?
In a primary allergy, the immune system reacts directly to a specific substance, such as birch pollen. A cross-allergy is a secondary reaction: The body has already developed a sensitization (i.e., an allergy) and now also reacts to other substances that are structurally similar.
Example:
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Primary allergy: birch pollen
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Cross-allergy: apple, hazelnut, celery
How common are cross allergies?
Cross-allergies are not uncommon. Approximately 60% of people with pollen allergies also develop cross-reactions to certain foods or substances over the course of their lives. Cross-allergies are particularly common in people with hay fever, for example, to birch, mugwort, or grasses.
Common symptoms of cross-allergy
Cross-allergies often affect the mucous membranes in the mouth and throat. Symptoms usually appear immediately after consuming the allergenic food—often within just a few minutes.
Typical symptoms are:
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Itching or tingling in the mouth, lips and palate
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Swelling of the lips, tongue or throat
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Redness in the mouth area
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sore throat
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Indigestion (rare)
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rash
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Breathing problems (in severe cases)
In very rare cases, an allergic shock (anaphylactic reaction) can occur – for example, in the case of cross-allergies with nuts or soy.
How is a cross-allergy diagnosed?
Diagnosis is usually made by an allergist. It begins with a detailed medical history and is supplemented by various tests:
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Prick test: Allergens are applied to the skin and lightly scratched.
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Blood test (RAST): Measures specific IgE antibodies against certain allergens.
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Provocation test: The suspected food is consumed under medical supervision.
Modern diagnostics also use so-called molecular allergy diagnostics , which specifically searches for reactive proteins in order to better limit cross-reactions.
What to do if you have a cross-allergy? Treatment and everyday tips
The most important measure is to avoid the triggering substances – however, this is often not so easy. Many people don't want to give up their favorite fruits. But there are ways to deal with cross-allergies.
1. Avoidance or preparation?
Some allergenic proteins are heat-sensitive . This means that if you cook an apple, for example, it loses its allergenic effect.
Examples of heat-sensitive cross-allergens:
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Apple → cooked mostly tolerated
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Carrots → cooked often no problem
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Cherries → as compote or jam uncritical
Other allergens are heat-stable (such as celery, soy, nuts) – the only solution here is to avoid them.
2. Antihistamines for acute symptoms
For milder reactions, antihistamines can help alleviate the allergic reaction. They are available over the counter at pharmacies, but should not be taken continuously.
3. Hyposensitization
For severe pollen allergies, specific immunotherapy (desensitization) can help. This involves slowly acclimating the immune system to the allergen. This therapy can also reduce the likelihood of cross-allergies.
Cross-allergy table: Overview of the most common cross-reactions
| Primary allergen | Typical cross allergies (food) |
|---|---|
| Birch pollen | Apple, hazelnut, cherry, kiwi, carrot, celery, soy, peach, almonds |
| Mugwort pollen | Celery, carrot, parsley, paprika, anise, fennel, cumin, mango |
| Grass pollen | Wheat, rye, tomato, peanut, soy, pulses |
| Latex (rubber) | Avocado, banana, kiwi, chestnuts, fig |
| House dust mites | Shellfish (crabs, shrimps), snails |
| Ragweed pollen | Banana, melon, zucchini, cucumber, sunflower seeds |
| Olive pollen | Tomato, peach, melon, kiwi |
This table will help you better control your diet – especially during hay fever season.
Cross-allergy in children: Special caution required
Children with hay fever or atopic dermatitis are at increased risk for cross-allergies. Pay attention to the following:
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The first signs are often tingling or a rash after eating.
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Don’t give up entire food groups too quickly – this can lead to nutritional deficiencies.
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Have the allergy checked professionally.
Tips for everyday life with cross-allergies
A few tried-and-tested strategies will help you cope with everyday life despite cross-allergies:
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Keep a diary: Note when and how you react to certain foods.
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Be aware of regional differences: Imported fruits often contain different allergen patterns.
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Pay attention to labels: Especially with processed products (e.g. soy lecithin, celery salt).
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Inform restaurants: When ordering, tell them what allergies you have – this will protect you from unknowingly ingesting them.
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Cook instead of eating raw: Many fruits and vegetables are safe when cooked.
What you should consider when shopping
Many convenience foods contain hidden allergens. Look carefully for the following ingredients:
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Soy in sauces, spreads, tofu, margarine
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Celery in soups, spice mixes, ready meals
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Nuts in muesli, bars, baked goods
In the EU, labeling is mandatory for the 14 most common allergens – use this to your advantage when shopping.
Avoiding cross-allergies – is that even possible?
Unfortunately, cross-allergies cannot be completely prevented. However, you can reduce your risk:
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Early and targeted treatment of hay fever
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No unnecessary avoidance of foods in childhood (according to current studies)
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Healthy nutrition to strengthen the intestinal flora and the immune system
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If you have known allergies, consult a doctor in good time before further allergies develop
When should you urgently see a doctor?
Be sure to seek medical help if you:
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you get shortness of breath after eating
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experience circulatory problems
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Swelling in the throat and pharynx occurs
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feel like your reactions are increasing
An allergy passport and an emergency kit (with adrenaline auto-injector) can be life-saving.
Conclusion: Recognize cross-allergies and live safely
Cross-allergies are common, but there's no reason to panic. With the necessary knowledge, medical support, and a few adjustments to your daily routine, you can live a symptom-free and still enjoy your life.
The key lies in a conscious examination of your body , targeted diagnostics , and proper food handling . Don't let yourself be limited – become the expert in your own health.
