title: Allergic host defences.
abstract: Allergies are generally thought to be a detrimental outcome of a mistargeted immune response that evolved to provide immunity to macroparasites. Here we present arguments to suggest that allergic immunity has an important role in host defence against noxious environmental substances, including venoms, haematophagous fluids, environmental xenobiotics and irritants. We argue that appropriately targeted allergic reactions are beneficial, although they can become detrimental when excessive. Furthermore, we suggest that allergic hypersensitivity evolved to elicit anticipatory responses and to promote avoidance of suboptimal environments.
authors.affiliation: Howard Hughes Medical Institute, Department of Immunobiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
authors.forename: Noah W
authors.initials: NW
authors.lastname: Palm
authors.forename: Rachel K
authors.initials: RK
authors.lastname: Rosenstein
authors.forename: Ruslan
authors.initials: R
authors.lastname: Medzhitov
mesh_terms: D000485:Allergens / Q000009:adverse effects / Q000276:immunology; D000818:Animals; D005075:Biological Evolution; D004781:Environmental Exposure; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology*; D007249:Inflammation / Q000276:immunology; D018448:Models, Immunological; D018418:Th2 Cells / Q000276:immunology*; D015262:Xenobiotics / Q000009:adverse effects / Q000276:immunology
chemical_list: D000485:Allergens; D015262:Xenobiotics