Proposed mechanism(s) | Characteristics |
IgE-mediated activation of mast cells and basophils Examples: Reactions to penicillin and other beta-lactams and to neuromuscular-blocking agents | - Can be evaluated with skin tests and/or in vitro tests for allergen-specific IgE
- Requires prior exposure to allergen or cross-reacting allergen
- Amenable to desensitization in some situations
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Immunologic mechanisms NOT involving IgE (mediated by IgG or IgM, antigen:antibody complexes, and/or complement) Examples: Reactions to dextran, protamine | - Formerly called anaphylactoid reactions
- Skin testing and in vitro IgE testing are NOT useful
- Pretreatment with glucocorticoids and/or antihistamines may be helpful
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Direct (nonimmunologic) activation of mast cells and basophils Examples: Reactions to radiocontrast agents, opioids, and to neuromuscular-blocking agents | - Formerly called anaphylactoid reactions
- Skin testing and in vitro IgE testing are NOT useful
- Pretreatment with glucocorticoids and/or antihistamines may be helpful
- Slow administration of responsible agent generally minimizes reactions
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