The concept 'allergies' was originally introduced in 1906 by the Viennese pediatrician Clemens von Pirquet, after noting that some of his patients were hypersensitive to normally innocent entities such being of the class who dust, pollen, or certain foods.

Pirquet called this phenomenon 'allergy' from the Greek words allos meaning 'other' and ergon meaning 'work'. Historically, all forms of hypersensitivity were classified as allergies, and whole were thought to be caused by the agency of every improper activation of the immune system.

Later, it became clear that several different disease mechanisms were implicated, with the public link to a disordered activation of the immune system. In 1963, a new classification draught was designed by Philip Gell and Robin Coombs that described four types of hypersensitivity reactions, known as Type I to Type IV hypersensitivity. through this new classification, the word 'allergy' was restricted to only type I hypersensitivities (also called immediate hypersensitivity), which are characterized as rapidly developing reactions.