|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. 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.
High-impact journals are those considered to be highly influential in their respective fields. The impact factor of journal provides quantitative assessment tool for grading, evaluating, sorting and comparing journals of similar kind. It reflects the average number of citations to recent articles published in science and social science journals in a particular year or period, and is frequently used as a proxy for the relative importance of a journal within its field. It is first devised by Eugene Garfield, the founder of the Institute for Scientific Information. The impact factor of a journal is evaluated by dividing the number of current year citations to the source items published in that journal during the previous two years.