What is allergy?

Allergy or allergic disease is a complex biological phenomenon, the basis of which is an immunological interaction between antibodies or sensitized cells that an individual has produced against more or less common, usually harmless substances, called allergens. The interaction causes a reaction that releases a series of chemical mediators that act on the patient's own organism and cause characteristic symptoms and signs: urticaria, asthma, rhinitis, anaphylaxis.
Allergy has been defined as an abnormal and autoaggressive form of immune reaction that occurs against pollen proteins, fungal spores, microscopic mites, mammalian epithelia, drugs, foods and many other products, which in themselves are not harmful. These are hypersensitivity reactions, most of them due to the production of antibodies by an immunoglobin, present in all human beings in very low concentration, called IgE (immunoglobin E).
Allergy has been known since ancient times (there is even evidence of an ancient Egyptian pharaoh who died of anaphylactic shock after being stung by a bee). It is a human disease, with a genetic basis, and its increase has been constant in the last decades. It is accepted that in Spain 20% or more of the population is allergic and its progression continues to increase, particularly in developed countries.
Allergology is a recognized medical specialty that is currently accessed through the MIR (medical intern resident) system of the national health system. Allergists or allergy physicians are responsible for establishing the diagnosis of an allergic disease as well as indicating and supervising the treatment of the disease.