A hypersensitivity reaction is an inappropriate or exaggerated response to an antigen or an allergen. The traditional classification for ...ForYouNews&PerspectiveDrugs&DiseasesCME&EducationAcademyVideoDecisionPointEdition:ENGLISHDEUTSCHESPAÑOLFRANÇAISPORTUGUÊSLogInSignUpIt'sFree!Edition:ENGLISHDEUTSCHESPAÑOLFRANÇAISPORTUGUÊSRegisterLogInNoResultsNoResultsForYouNews&PerspectiveDrugs&DiseasesCME&EducationAcademyVideoDecisionPointclosePleaseconfirmthatyouwouldliketologoutofMedscape.Ifyoulogout,youwillberequiredtoenteryourusernameandpasswordthenexttimeyouvisit.LogoutCancelhttps://profreg.medscape.com/px/getpracticeprofile.do?method=getProfessionalProfile&urlCache=aHR0cDovL2VtZWRpY2luZS5tZWRzY2FwZS5jb20vYXJ0aWNsZS8xMzYyMTctb3ZlcnZpZXc=processing....Drugs&Diseases>Allergy&ImmunologyImmediateHypersensitivityReactionsUpdated:Aug11,2020Author:BeckyBuelow,MD,MS;ChiefEditor:MichaelAKaliner,MD more...ShareEmailPrintFeedbackCloseFacebookTwitterLinkedInGoogle+SectionsImmediateHypersensitivityReactionsSectionsImmediateHypersensitivityReactionsOverviewBackgroundPathophysiologyEpidemiologyShowAllPresentationHistoryPhysicalCausesShowAllDDxWorkupLaboratoryStudiesOtherTestsShowAllTreatmentMedicalCareConsultationsDietShowAllMedicationMedicationSummaryVasopressorsBronchodilatorsCorticosteroidsHistamine1receptorantagonists(antihistamines)Histamine2receptorantagonists(H2antagonists)LeukotrieneinhibitorsImmunomodulatorsMonoclonalAntibodies5-LipoxygenaseInhibitorsShowAllFollow-upDeterrence/PreventionPatientEducationShowAllTablesReferencesOverviewBackgroundTheimmunesystemisanintegralpartofhumanprotectionagainstdisease.Thenormallyprotectiveimmunemechanismscansometimescausedetrimentaleffectsinthehostcalledhypersensitivityreactions.Ahypersensitivityreactionisaninappropriateorexaggeratedresponsetoanantigenoranallergen.ThetraditionalclassificationforhypersensitivityreactionsisthatofGellandCoombsandiscurrentlythemostcommonlyknownclassificationsystem.[1]Itdividesthehypersensitivityreactionsintothefo