View source for Hypersensitivity reaction

==Background==
*Uncomfortable, damaging, and sometimes fatal reactions produced by the normal immune system including allergies and autoimmunity. 

==Clinical Features==
{| class="wikitable"
|-
! Type !! Mechanism !! Example
|-
| I: Allergy, Immediate || IgE-mediated degranulation of mast cells and basophils; usually happens after a first exposure which causes sensitization || [[Urticaria]], [[anaphylaxis]], [[angioedema]]
|-
| II: Cytotoxic, Antibody Dependant || IgG or IgM antibodies react with cell antigens with resultant complement activation || [[Myasthenia gravis]], [[goodpasture syndrome]], erythroblastalis fetalis, AI hemolytic anemia, Graves disease
|-
| III: Immune Complex || IgG immune complex deposition and subsequent complement activation || [[Serum sickness]], RA, [[SLE]], [[poststreptococcal glomerulonephritis]]
|-
| IV: Cell-mediated, Delayed || Activated T cells against cell surface antigens || TB skin test, chronic transplant rejection, delayed drug rashes, [[contact dermatitis]]
|}

==See Also==
*[[Acute allergic reaction]]

==References==
<references/>

[[Category:Dermatology]] [[Category:Rheumatology]]