Cross allergy

In a cross allergy people react allergic to several substances. Often these are found in foods. Learn more!

Cross allergy

At a cross allergy it is a food allergy. It is triggered because the subjects also have an allergic reaction 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 doctor's letters or on incapacity certificates. L23J30

Product Overview

cross allergy

  • description

  • symptoms

  • Causes and risk factors

  • Examinations and diagnosis

  • treatment

  • Disease course and prognosis

Cross allergy: description

If patients with allergies to pollen, grasses, 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 are more likely to trigger 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 harmless substances. The allergens can consist of vegetable or animal proteins and are usually harmless. In case of an allergy, however, 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.

Cross allergy: symptoms

Frequently, a cross-allergy is mild and 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 when eating a so-called urticaria. Urticaria is a collection of wheals on the most 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

Cross allergy: causes and risk factors

The cross allergy is triggered by components of the food. The immune system of those affected 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 settle 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 person has taken up, the more pronounced the reaction is, is local 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. The proteins can be related to each other, for example, since they originated 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 increasingly released from the so-called mast cells in an allergic reaction 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

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 were the symptoms?
  • Do you suffer from eczema, allergic asthma or hay fever?

Then a prick test is performed. The prick test is an allergy test in which the upper skin layer is first slightly scratched. Subsequently, allergen solutions are applied on 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, an antibody determination is also 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.

Cross allergy: treatment

Medication reduces the symptoms of the cross allergy, the allergy itself can only be treated by a so-called hyposensitization. Hyposensitization is a lengthy treatment that can, however, ideally make the patient symptom-free.


In order to treat the symptoms of the allergic reaction, various medications are available in tablet form, as inhalation sprays, ointments or injections. Antihistamines such as cetirizine can stem the effect of histamine by blocking histamine receptors in the body.

Glucocorticoids such as prednisolone inhibit the immune system. As a result, an allergic reaction can take place only limited or completely prevented. Prednisolone is given along with antihistamines and epinephrine, for example, in an anaphylactic shock in an allergy.

So-called mast cell stabilizers such as cromoglycine prevent histamine from being released from mast cells. The allergic reaction can be contained.

Avoid allergens

If a cross-allergy has been confirmed, one should avoid the food or otherwise prepare it. When heated, most proteins lose their allergenic effects. Carrots that are eaten raw can trigger an oral allergy syndrome, for example, cooked well. In addition, the allergic reaction to cross-reactive foods after the pollen season from March to late August is often milder.

Since patients who are allergic to several foods still need a balanced diet, a nutritional plan should be prepared with the attending physician.

A cross allergy can lead to life-threatening circulatory problems. It is therefore particularly important that the persons affected are informed about their illness. They should know how to behave in the event of an allergic reaction and always carry an allergy passport and an allergy emergency bag with medication.

Read more about the investigations

  • allergy test

Cross allergy: disease course and prognosis

The severity of a cross allergy varies. Some patients with pronounced pollen allergy respond only slightly to a particular food. On the other hand, a pollen allergy can be associated with very little discomfort. Those affected who may not yet be aware of their pollen allergy experience a severe allergic reaction after consuming a cross-reactive food. Cross-overergy can sometimes get worse over years or more and more food. On the other hand, there is also the possibility that it disappears by itself after some time.

The expression of a cross reaction varies with the season, pollen and environmental toxins to which the person is exposed. The mental state also plays a role in the symptoms.


To delimit from the cross-allergies are the so-called pseudoallergies on food. They are not allergic reactions in the true sense. The symptoms are very similar to those of the cross allergy to food, but appear slightly later after food intake and last longer. The prick test and the IgE antibody determination are negative. Hyposensitization is ineffective.

Cross allergy: prevent

In general, it is important to treat the causative allergy. Why allergies arise is not fully understood until today, but the risk factors listed above are considered assured. If you suffer from a cross-allergy, you should avoid the foods involved or prepare them differently.

Also, you should enjoy foods that are also associated with a cross-allergy, with caution. For example, if you suffer from a latex allergy and show symptoms of an oral allergy syndrome after eating a kiwi, it is advisable not to consume fresh avocados.

A healthy lifestyle and physical exercise strengthen the immune system. The symptoms of allergies are thereby diminished and the appearance of a cross allergy possibly even prevented.

Read more about the therapies

  • Hyposensibilisierung
  • nasal douche

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