Cross allergy


At a cross allergy it is a food allergy. It is triggered because those affected are also allergic to similar substances (such as pollen, grasses, latex). The symptoms of cross-allergy are often limited to the mouth area. But it can also cause severe allergic reactions that affect the entire body. Read all about cross allergy here, when it is dangerous and how to avoid it.

ICD codes for this disease: ICD codes are internationally valid medical diagnosis codes. They are found e.g. in medical reports or on incapacity certificates. L23J30ArtikelübersichtKreuzallergie

  • description
  • symptoms
  • Causes and risk factors
  • Examinations and diagnosis
  • treatment
  • Disease course and prognosis

Cross allergy: description

If patients with allergies to pollen, grass, latex or dust are suddenly allergic to food, it is called cross-allergy. Often the symptoms are mild. However, in some cases, severe reactions may occur to certain foods that affect the entire body. Some foods cause more frequent cross-allergy. These include hazelnuts, peanuts or celery. The incidence of cross-allergies tends to increase in Germany.

An overreaction of the immune system

In an allergy, the immune system is directed against actually safe substances. The allergens can consist of vegetable or animal proteins and are usually harmless. In case of an allergy, the immune system does not recognize the substances as harmless and fights them. The allergic reaction is therefore always an excessive defense reaction.

A disease caused by an excessive immune response is also called atopic disease. Many patients with cross-allergies also suffer from other atopic diseases such as hay fever, allergic asthma or atopic dermatitis.

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Cross allergy: symptoms

Often a cross allergy runs mild and is limited to a specific body region. The symptoms of cross-allergy usually occur from a few minutes to two hours after ingestion.

In adults, who suffer from a cross allergy, arises in the oral mucosa usually after or at food intake a so-called urticaria. Urticaria is a build-up of wheals on the mostly reddened skin. The oral mucosa burns, itches and the tongue tingles. The symptoms are also referred to as "oral allergy syndrome". Furthermore, the following complaints may occur in the mouth area:

  • Itching: on the lips, on the tongue, on the palate, on the ears, in the throat
  • Swelling of the oral mucosa
  • Skin redness on the oral mucosa and around the mouth
  • Blistering especially on the lips

In rare cases, the cross-allergy can affect the entire body. Most often, the skin is affected. It responds with the following symptoms:

  • Whealing all over the body with itching (hives)
  • sudden severe "doughy" swelling of the skin, so-called angioedema
  • Flush symptoms: sudden severe redness of the skin sometimes along with itching
  • Deterioration of eczema in patients with atopic dermatitis
  • Diseases of the gastrointestinal tract such as vomiting or diarrhea
  • difficulty in breathing
  • Circulatory problems such as dizziness and drop in blood pressure
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Cross allergy: causes and risk factors

The cross allergy is triggered by components of the food. The immune system of those affected initially becomes "sensitive" to some proteins of plants and animals and forms certain antibodies. At the next contact with the special proteins, the immune system reacts by means of the antibodies produced with a defense reaction. The antibodies sit on their surface and try to make the proteins harmless. Depending on how strongly the immune system has been sensitized and how many allergens the affected person has absorbed, the more pronounced the reaction is, is locally limited or affects the entire body.

Proteins are similar

In the case of cross allergy, the immune system now also reacts to proteins that only resemble the original allergens. For example, the proteins may be related to each other since they were formed many years ago from a common protein. Because they resemble each other in their structure, the antibodies formed also fit on their surface. So it is not only between pollen and food to cross-allergies, but also between individual foods such as fish or shellfish.

An endogenous messenger substance that also plays an important role in the allergic reaction is histamine. Histamine is released in an allergic reaction increasingly from the so-called mast cells and triggers various allergic symptoms. In asthmatics, for example, it can trigger an asthma attack.

Every person can develop an allergy in the course of his life and thus a cross allergy. However, there are several factors that increase the risk of an allergy to illness. These include:

  • genetic preloads
  • high-fat diet, fast food, food contaminated with dyes and preservatives
  • Smoke
  • air pollution
  • excessive hygiene
  • Non-breastfeeding in infants

Cross allergy table

A cross-allergic table can provide an overview of the cross-reacting allergens.

Known or existing allergy


Cross allergy with

Cross allergy "birch" ("birch pollen nut kernel fruit syndrome")


Carrot, soy, celery, apple, hazelnut, fresh stone fruit, kiwi

Cross allergy "grasses"

grass pollen

Pulses (peanut, soy), cereal flour

Cross allergy "mugwort" ("celery-carrot-mugwort-spice syndrome")

mugwort pollen

Celery, carrot, potato, spices (aniseed, curry, cinnamon)

Cross allergy "latex" ("latex-fruit syndrome")


Avocado, banana, kiwi

Cross allergy "house dust mites"


Cup / crustaceans

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Cross allergy: examinations and diagnosis

If a cross-allergy is suspected, the doctor first asks about known allergies such as hay fever or house dust allergies. The following questions could also be asked:

  • Is an allergy known to you?
  • What are you allergic to?
  • Is your oral mucosa swollen?
  • Did you have a rash?
  • When exactly did the symptoms occur?
  • Do you suffer from eczema, allergic asthma or hay fever?

Subsequently, a prick test is performed. The prick test is an allergy test in which the upper skin layer is first minimally scratched. Subsequently, allergen solutions are applied to the scored skin areas. After five to 60 minutes, in the case of an allergy, a local reaction, such as redness of the skin, can occur on the allergen. The prick test is then positive.

As an alternative to the prick test also an antibody determination is possible. This cross-reactive antibodies are detected in the blood of the patient.

The oral provocation test is performed after a positive prick test. The person concerned takes the suspicious food under medical supervision. This shows how the body of the patient responds to the supplied allergens.