The immune system defends our body against foreign substances
Our immune system defends our body against foreign substances, thus protecting it against all manner of pathogens and other unwanted intruders. It has a special identification mechanism of its own: what is natural and what is foreign? If a substance occurs naturally in the body, the immune system will normally not react. If a foreign substance is detected, the immune system will be activated. It will attack and, if possible, annihilate the foreign substance with an impressive army of cells. In the case of an allergic reaction, the immune system is 'mistaken'. It overreacts to a harmless substance in pollen, for example. Our immune system is an ingenious and complex mechanism.
In fact, it is so complex that an occasional error is not even that surprising. An allergy is the result of such an error. The system reacts to a harmless substance as though it were a harmful substance. Once the reaction has been triggered, it will cause a snowball effect. The body produces antibodies and, as a result, releases other substances such as histamines, which can cause allergic symptoms. The immune response often spreads across the body, inducing several symptoms at the same time. These include watery eyes, runny nose, sneezing or skin rash, as the histamines are released at various locations in the body where they cause inflammatory reactions.
Allergens may intrude into the body wherever it has contact with the outside world. By inhalation, via the skin, the digestive tract, injections, medication, insect stings. The type of allergic reaction depends on where the allergen enters the body and the type of immune cells that are activated.