TYPE%1%HYPERSENSITIVITY%
Key%Points%
1. IgE%attached%to%mast%cells%mediates%type%1%hypersensitivity%reactions%
• Reactions%develop%within%seconds%or%minutes%after%exposure%to%antigen%(Ag)%
%
2. Clinical%signs%(acute%inflammation%and%systemic%effects%caused%by%rapid%degranulation%of%mast%cells%that%
occurs%once%Ag%binds%and%cross-links%two%IgE%molecules,%causing%release%of%vasoactive%molecules,%
chemotactic%molecules,%enzymes%and%cytokines%
%
%
%
3. Severity%and%location%of%clinical%signs%depends%on%number%and%location%of%mast%cells,%basophils,%
eosinophils,%which%depends%on%degree%of%sensitization%of%animal,%amount%of%antigen%involved%and%route%
of%administration%
!
Specific!allergic!conditions!!
• Food%allergy%
• Allergic%inhalant%dermatitis%
• Atopic%dermatitis%
• Allergies%to%vaccines%and%drugs%
• Allergies%to%parasites:%sarcoptes%scabiei%dogs,%octodectes%cyanotis%in%cats%
i. Flea%allergy%dermatitis%may%also%be%type%IV%HS%mediated%
• Eosinophilic%granuloma%complex%(cats)%
!
Allergic!anaphylaxis%
• Severe,%life%threatening%generalized%or%systemic%hypersensitivity%reaction%
• Clinical%signs%determined%by%organ%involvement%and%differs%among%species%
• Symptoms%are%result%of%vasoactive%molecules%contracting%smooth%muscle%of%bronchi,%GIT,%uterus%
and%bladder%
%
