What Is Cross Allergy / Allergy Cross Reactivity?

Allergies were relatively rare in the 19th century, but the rapidly developing society of the following century led to their increase. The rise of synthetic materials, air pollution, and environmental degradation from industrialization brought allergies to the forefront. Today, 40% of Europeans suffer from some form of allergy, and the number is only growing. What is a cross allergy, and what does it mean?

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What Is Combined or Cross-Allergy / Allergy Cross Reactivity?

Cross allergy  occurs when the body's immune system identifies the proteins in one substance (pollen) and the proteins in another (a fruit or vegetable) as being similar. A combined or cross-allergy is a type of allergic reaction that occurs when an individual is allergic to more than one substance. This can happen when the individual is allergic to a substance, such as pollen, and then develops an allergy to a different substance, such as a certain type of food, that has similar proteins to the original allergen. 

When the body's immune system encounters the new allergen, it reacts as if it were the original allergen and produces antibodies to fight it off. This can lead to symptoms such as sneezing, itching, watery eyes, and difficulty breathing.

In some cases, a allergy cross reactivity can be severe and even life-threatening, such as in the case of a nut allergy. An individual who is allergic to nuts may also develop an allergy to certain fruits and vegetables that have similar proteins, putting them at risk of a severe reaction if they eat those foods.

The Most Common Combined Reactions Occur:

  • Between foods
  • Between a food and an inhaled allergen, such as pollen or dust mites
  • Between latex and a food

Did you know that allergies to fruits and vegetables only occur when they are consumed raw? When they are cooked, boiled, or heated in a microwave, the allergens are destroyed and the individual is not at risk of a reaction. This is not the case for other foods, as heating them does not always destroy the allergens. For example, heating goat's milk does not prevent an allergic reaction in an individual with a goat's milk allergy. There are also some exceptions, such as parsley, celery, spices, nuts, and peanuts, whose allergens are more resistant to heat.

Tip: Read everything about the calendar for allergy sufferers and find out which allergens to watch out for throughout the year.

Symptoms of Cross-Allergy

Allergies are called local or systemic reactions to allergens. Systemic reaction, or anaphylaxis, is a serious allergic reaction that occurs very quickly and can even cause death. It is usually a set of suddenly occurring allergic symptoms, in several organs - for example, a skin reaction, narrowing of the bronchi in the respiratory tract, suffocation and swelling, in the digestive tract, in the cardiovascular tract a decrease in blood pressure, in the urogenital tract. Anaphylaxis can be caused by food, drugs or insect venom. It requires timely initiation of therapy. If it is a life-threatening condition, we speak of anaphylactic shock.


Tip: Download the nanoSPACE pollen calendar in pdf and be prepared for the pollen season.

Local Symptoms of Allergies Include Mainly:

  • Swelling of the nasal mucosa
  • Swelling of the eyes
  • Itching
  • Difficulty breathing
  • Earache
  • Eczema
  • Hives
  • Even headaches

Home Allergy Test

Allergies are usually diagnosed with allergy tests. Before you make an appointment there, you can do a home allergy test. To perform the test, a drop of blood is taken by lancet from the finger, from which IgE antibodies are detected. The test detects allergies to dust mites, pollen, and cat hair. The advantage of the test is its speed and ease of use. The test result is known within 15 minutes. The instructions for use are attached to it.

How Cross-Allergy Manifests: Pollen - Food

In the case of cross-allergy between pollen and food, we speak of oral allergy syndrome. It usually occurs when raw fruit or vegetables are consumed, and within a few minutes the affected person begins to feel a burning sensation in the lips, palate, tongue, or throat. Itching or swelling may appear around the lips. If the person continues to eat the fruit or vegetables that caused the reaction, the symptoms will worsen, such as eye inflammation, asthma, rhinitis, swelling of the larynx, or anaphylaxis.


In some cases, the occurrence of a pollen-food cross-reaction is only associated with the pollen season, when allergy sufferers cannot eat kiwi during the birch flowering season, but at other times it does not cause them any problems. Allergies can also be caused by simply touching, for example, when rubbing your eyes when peeling, slicing, or grating fruit and vegetables.

Tip: Read the article on how to prepare for the allergy season.

Common Types of Allergy Cross Reactivity




pear, apple, peach, nectarine, cherry, plum, apricot, kiwi, carrot, celery, parsley, potato, hazelnut, walnut, peanut


wheat, apple of paradise


banana, watermelon, honeydew melon, pineapple melon, chamomile tea


carrots, celery, parsley, spices - fennel, cumin, dill, anise, cloves


figs, kiwi, pineapple, banana, avocado


How to Protect against the Onset of Allergies

Once you have been diagnosed with an allergy, you will have to learn to live with it. It will be important for you to limit your exposure to allergens, not only outside but also at home. If you have pollen allergies, you may have to forget about going for a walk in a field full of beautiful flowers, admiring the fresh flowers on trees, or lying down in fresh hay in a hayloft.

Tip: How to fight pollen allergies in the spring? You will find out in our article.

On a walk outside during the pollen season, you will probably wear glasses and have antihistamines in your pocket (medications, nasal sprays or filters for the nose and eye drops). Morning and evening walks will be more suitable. Upon returning home, it is advisable to perform a nasal lavage to get rid of allergens deposited on the mucous membranes. Windy weather will be a disaster for you. At home, you should ventilate in the morning, evening, and after rain, when there are fewer allergens outside. You cannot bring flowering or dried plants into the house. The apartment must be kept clean, the floors regularly mopped, carpets vacuumed, and the air cleaned.


When allergic to dust mites, you can purchase special anti-allergy blankets, pillows, linen, sheets, and mattress protectors. It is definitely worth investing the money, as you are doing it for your own health. Bed linen must be kept clean and bedding washed regularly.

In the case of cross-allergy, it is necessary to omit the food that could cause allergic problems. You should also inform your immediate environment and close ones about this fact. Be careful in restaurants and ask for information about allergens in the food you have ordered.

It is a given to follow the treatment plan proposed by your allergist. Any uncertainties must be consulted with him. Read also: Nasal Irrigation: Everything You Need to Know

Learn More About Allergies:



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Lucie Konečná, from nanoSPACE
Lucie Konečná has been working in the field of nanotechnology for 7 years. She is a co-author of the Czech is Nano project and has been involved in building public awareness of nanotechnology. Lucie has been managing operations of the nanoSPACE e-shop since May 2020.