Allergy Classification
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Type I
 - immediate, atopic, reaginic, anaphylactic, IgE-mediated,
   humoral hypersensitivity
 - examples: urticaria, angioedema, anaphylaxis

Type II
 - cytotoxic reactions, cytolytic complement-dependent cytotoxicity,
   cell-stimulating reactions
 - examples: hemolytic anemia, thrombocytopenic purpura, pemphigus,
   pemphigoid, myasthenia

Type III
 - immune complex, soluble immune complex hypersensitivity reactions,
   toxic complex reactions
 - examples: serum sickness, rheumatoid arthritis, polyarteritis,
   cryoglobulinemia, hypersensitivity pneumonitis, acute glomerulonephritis,
   Arthus reaction.

Type IV
 - cellular, cell-mediated, delayed, or tuberculin-type hypersensitivity
   reactions
 - examples: contact dermatitis, allograft reaction, some drug reactions
 - usually delayed by 24-48 hours