Allergies in the modern world are very widespread. Allergy sufferers usually know what the reaction is to and try to eliminate the component that causes the allergy. It seems to be a clear story. However, there is often an unexpected reaction to substances that are not allergens and have long been familiar to the body. How is this possible and why? Today we will talk about cross-allergy using birch as an example.
How does allergy develop?
Allergy is an increased immune response to common irritants. A person observes the development of a violent reaction immediately after contact with an allergen. It can be skin rashes, runny nose, sneezing, lacrimation, cough, in severe cases – shortness of breath, Quincke’s edema and anaphylactic shock. In fact, a meeting with an allergen occurred earlier, the immune system mistakenly recognized it as a particularly dangerous protein for the body and began to prepare an “army” – to produce immunoglobulins E (IgE). IgE binds to mast cells, which contain histamine and other toxic substances. Everything is ready for the attack. And as soon as the allergen enters the body, a reaction immediately occurs – the release of histamine by mast cells. Hence the “suddenness” of the allergic reaction. And the stage of preparation for the reaction is called sensitization.
What you need to know about allergens?
Any allergen has a complex structure, it contains many proteins, and the immune system recognizes each of them separately. It turns out that each protein in one allergen is itself an allergen and its own IgE is produced to it. Birch in Latin Betula verucosa, and abbreviated as Bet v. The proteins that make up it are designated Bet v1, Bet v2, and so on, and IgE is determined for each of them. Bet v1 is called the main allergy component, or major.
What Happens With Cross-Allergy?
Proteins of different allergens have a similar structure. The immune system is a finely organized structure, not a printing press. The phenomenon of erroneous recognition not of the allergen molecule itself, but of other proteins that are similar in structure, but from a different source, is called cross-allergy. Most often observed on birch pollen. Birch and many fruits may have a molecular similarity of up to 70%, so if you are allergic to tree pollen, a reaction to apples may develop, for example. That is, when eating an apple, sneezing or itching of the skin appeared, and there may also be discomfort in the mouth, numbness, and burning. It’s just that the immune system is sure that a molecule of pollen (and not an apple) has entered the body and is attacking it.
What foods can be potential allergens?
Proteins similar to Bet v1 (Bet v1 homologues) are the most active; they belong to the whole protein family (PR-10). Contained in the following fruits and vegetables:
Apple, cherry, peach (from the Rosaceae family)
Carrots, celery, parsley (umbrella family)
Soybeans, peanuts (legume family)
Proteins similar in structure to Bet v2 (profilins) – timothy (Phl p12), peach, latex (rubber gloves). Also found in apples, cherries, soybeans, peanuts; plus in hazelnuts and tomatoes.
Proteins similar to Bet v4 are found in timothy pollen (Phl p7).
How can you suspect cross-allergy to birch pollen?
The manifestations are most typical for the first group of proteins – Bet v1 homologues. Oral allergy syndrome develops:
Link to eating fresh fruits and vegetables
A sharp appearance in the first minutes after consumption, very rarely – within an hour
There is swelling, itching, pain, burning, tingling in the lips, gums, palate, tongue
Red spots around the mouth, on the neck
Lacrimation, sneezing, profuse runny nose, swelling of the eyelids are possible.
Asthma attacks and Quincke’s edema were recorded in 1-2% of cases.
But most often, the signs are short-lived and disappear on their own, which makes it difficult to diagnose for the following reasons:
Patients know that they are allergic to birch pollen, but do not know what cross-allergy is, so they cannot associate the complaints that arise with birch and ignore them or start looking for a “new” allergy on their own, wasting money.
Young children with sensitization to birch pollen (when the body is preparing for an attack) first develop symptoms of “oral allergy”, more often with the introduction of complementary foods. The kid cries, spits out food. And mom makes him eat, referring to whims. Thus, a serious allergy to birch pollen or bronchial asthma develops.
How to recognize cross-allergy?
As you already understood, only a competent allergist can understand the complex mechanisms of the immune system and many allergens https://en.wikipedia.org/wiki/Allergen. He collects complaints, finds out the connection with various allergens and prescribes additional research methods: skin tests and laboratory tests.