That is why you react to fresh tomatoes and not to cooked
The allergic reaction to certain foods is caused by an excessive reaction of the immune system to the foreign substance. Normally, there is an initial contact of the body with the substance, whereupon immune cells are formed which recognize certain surface proteins (proteins on the surface of the substance). At the second contact with the affected food, the immune system recognizes these surface proteins based on the immune cells that have already been formed.
This mechanism is actually intended as a defence against dangerous substances. In the case of an allergic reaction, however, the body reacts with an excessive immune response to a substance that is actually harmless. The key stimulus for the immune system is the recognition of the above mentioned surface proteins.
In a fresh tomato, these are configured in the same way as the immune system detected them on first contact. By heating the tomatoes, these surface proteins are also heated. This denatures the proteins, i.e. the surface proteins are destroyed by the heating or their shape changes. This means that the body’s immune cells can no longer recognize the tomato proteins and an immune reaction against the heated tomato does not occur.
Diagnosis of a tomato allergy
The diagnosis of tomato allergy is initially based on the medical history. The doctor will ask about the symptoms of the affected person. The temporal connection between the consumption of the tomato and the onset of symptoms such as itching, diarrhoea and nausea is particularly important.
If these symptoms can be clearly attributed to tomato consumption, no further diagnosis is necessary. However, in order to make a reliable diagnosis, the so-called prick test is used. This involves injecting a minimal amount of the tomato allergens under the skin of the affected person. Subsequently, in case of tomato allergy, a skin reaction in the form of redness, swelling and itching at the injection site is expected.
