Allergy is a disorder of the immune system that is often called atopy. Allergic reactions occur to environmental substances known as allergens; these reactions are acquired, predictable and rapid. Strictly, allergy is one of four forms of hypersensitivity and is called type I (or immediate) hypersensitivity. It is characterized by the agency of excessive activation of certain pure blood cells called mast cells and basophils by a pattern of antibody, known as IgE, resulting in an last fiery response. Common allergic reactions include eczema, hives, hay flush, asthma, food allergies, and reactions to the venom of stinging insects such like wasps and bees. Mild allergies like hay fever, are highly prevalent in the human population and account symptoms such to the degree that allergic conjunctivitis, itchiness and runny nose. Similarly, conditions such as asthma are frequent, in which allergy plays a major role. In some people, severe allergies to environmental or dietary allergens, or to medication, occur that may result in life-threatening anaphylactic reactions and potentially death. A variety of tests now exist to diagnose allergic stipulations; these include testing the skin for responses to known allergens or analyzing the blood for the presence and levels of allergen-specific IgE. Treatments for allergies embody allergen avoidance, use of antihistamines, steroids or other oral medications, immunotherapy to desensitize the response to allergen, and targeted therapy. Classification and history The concept 'allergy' 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. A major breakthrough in understanding the mechanisms of Allergies Online was the discovery of the antibody class labeled immunoglobulin E (IgE) - Kimishige Ishizaka and co-workers were the first to isolate and mark out IgE in the 1960s