ALLERGY AND IMMUNOLOGY

Types of allergic reactions:

• "Type I"-Eosinophil-mediated, immediate (minutes), systemic symptoms e.g. urticaria, angioedema, airway swelling, vascular collapse/shock.  Can be confirmed with serum IgE radioallergosorbent testing (RAST) (high-titer result has 50-90% sensitivity and 80-87% specificity). If negative, prick skin test is more sensitive but has risk of inducing a systemic reaction
• "Type IV"-T-cell-mediated, delayed (24-96h), local symptoms e.g. allergic contact dermatitis; little association with anaphylaxis.  Skin patch testing can cnofirm.

(Sources include Core Content Review of Family Medicine, 2012)