During an allergic reaction, the immune system reacts to normally harmless foreign substances such as pollen, medications, food, or animal dander. Although allergic reactions can principally take place in all organs, the primary target organs are the skin, respiratory system, gastrointestinal tract, and eyes. Depending on the organs involved, symptoms of allergic reactions include nasal congestion, eczema, pruritus, cough, chest tightness, wheezing, dyspnea, and vomiting. In case of anaphylaxis, a potentially fatal severe allergic reaction, cardiovascular changes resulting in hypotension and tachycardia can additionally occur. Allergic diseases are characterized by immune responses predominantly driven by T-helper-2 (Th2) cells, which activate many immune cells to produce and release different inflammatory mediators during an allergic reaction (see chapter “ Overview” under the part “Immune system”). Apart from allergen avoidance, the treatment principles are neutralization of these mediators particularly in the short term and restoration of immune balance between Th2 cells and other lymphocyte subsets like T-helper-1 (Th1) or regulatory T (Treg) cells in the long term. The risk factors include family history of allergy/genetic factors and environmental factors such as exposures to allergens and microbes. However, a number of studies show conflicting data for the latter, suggesting that the interaction of certain allergens and infectious agents with the immune system is complicated. Nonetheless, a dramatic increase in allergic diseases in industrialized countries over the last several decades implicates environmental factors as a major contributor. Allergic diseases affect up to 30 % of the population in these countries, resulting in high economical burden of the diseases.
KeywordsMast Cell Allergic Reaction Treg Cell Allergic Rhinitis Allergic Disease
- 5.Bousquet J, Anto JM, Demoly P, Schünemann HJ, Togias A, Akdis M, Auffray C, Bachert C, Bieber T, Bousquet PJ, Carlsen KH, Casale TB, Cruz AA, Keil T, Lodrup Carlsen KC, Maurer M, Ohta K, Papadopoulos NG, Roman Rodriguez M, Samolinski B, Agache I, Andrianarisoa A, Ang CS, Annesi-Maesano I, Ballester F, Baena-Cagnani CE, Basagaña X, Bateman ED, Bel EH, Bedbrook A, Beghé B, Beji M, Ben Kheder A, Benet M, Bennoor KS, Bergmann KC, Berrissoul F, Bindslev Jensen C, Bleecker ER, Bonini S, Boner AL, Boulet LP, Brightling CE, Brozek JL, Bush A, Busse WW, Camargos PA, Canonica GW, Carr W, Cesario A, Chen YZ, Chiriac AM, Costa DJ, Cox L, Custovic A, Dahl R, Darsow U, Didi T, Dolen WK, Douagui H, Dubakiene R, El-Meziane A, Fonseca JA, Fokkens WJ, Fthenou E, Gamkrelidze A, Garcia-Aymerich J, Gerth van Wijk R, Gimeno-Santos E, Guerra S, Haahtela T, Haddad H, Hellings PW, Hellquist-Dahl B, Hohmann C, Howarth P, Hourihane JO, Humbert M, Jacquemin B, Just J, Kalayci O, Kaliner MA, Kauffmann F, Kerkhof M, Khayat G, Koffi N'Goran B, Kogevinas M, Koppelman GH, Kowalski ML, Kull I, Kuna P, Larenas D, Lavi I, Le LT, Lieberman P, Lipworth B, Mahboub B, Makela MJ, Martin F, Martinez FD, Marshall GD, Mazon A, Melen E, Meltzer EO, Mihaltan F, Mohammad Y, Mohammadi A, Momas I, Morais-Almeida M, Mullol J, Muraro A, Naclerio R, Nafti S, Namazova-Baranova L, Nawijn MC, Nyembue TD, Oddie S, O'Hehir RE, Okamoto Y, Orru MP, Ozdemir C, Ouedraogo GS, Palkonen S, Panzner P, Passalacqua G, Pawankar R, Pigearias B, Pin I, Pinart M, Pison C, Popov TA, Porta D, Postma DS, Price D, Rabe KF, Ratomaharo J, Reitamo S, Rezagui D, Ring J, Roberts R, Roca J, Rogala B, Romano A, Rosado-Pinto J, Ryan D, Sanchez-Borges M, Scadding GK, Sheikh A, Simons FE, Siroux V, Schmid-Grendelmeier PD, Smit HA, Sooronbaev T, Stein RT, Sterk PJ, Sunyer J, Terreehorst I, Toskala E, Tremblay Y, Valenta R, Valeyre D, Vandenplas O, van Weel C, Vassilaki M, Varraso R, Viegi G, Wang DY, Wickman M, Williams D, Wöhrl S, Wright J, Yorgancioglu A, Yusuf OM, Zar HJ, Zernotti ME, Zidarn M, Zhong N, Zuberbier T (2012) Severe chronic allergic (and related) diseases: a uniform approach–a MeDALL–GA2LEN–ARIA position paper. Int Arch Allergy Immunol 158:216–231CrossRefPubMedGoogle Scholar