Hypersensitivity is the excessive, undesirable reactions produced by the normal immune system. Hypersensitivity reactions mediated by T cells can be activated by modified self proteins, or by injected proteins. Allergic hypersensitivity occurs when an individual, who has produced IgE antibody in response to an antigen, or allergen, gets exposed to the same allergen. Allergic hypersensitivity is immediate type hypersensitivity as it occurs seconds to minutes after allergen exposure and it may result in disorders like asthma, anaphylaxis, atopy. Allergens are nonparasite antigens that can stimulate a type I hypersensitivity response. These allergen triggers the activation of IgE-binding mast cells in the exposed tissue, leading to a series of responses that are characteristic of allergy. The most common allergens include airborne allergens such as grass, tree or weed pollen, as well as moulds. Scientific journal is a periodical publication intended to further progress of science, usually by reporting novel research. There are thousands of scientific journals in publication, and many more have been published at various points in the past. Most journals are highly specialized, although some of the oldest journals publish articles and scientific papers across a wide range of scientific fields. Scientific journals contain articles that are peer reviewed, to ensure that articles meet the journal's standards of quality, and scientific validity. The publication of the results of research is an essential part of the scientific method. If they are describing experiments or calculations, they must supply enough details that an independent researcher could repeat the experiment or calculation to verify the results.