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Acute allergic reaction
From WikEM
(Redirected from Allergen exposure)
Contents
Background
- Similar to Anaphylaxis but does not meet all the requirements (i.e. just skin manifestations)
- Type I hypersensitivity reaction
Clinical Features
- Presentation can be delayed
Differential Diagnosis
Acute allergic reaction
- Allergic reaction/urticaria
- Anaphylaxis
- Angioedema
- Asthma exacerbation
- Anxiety attack
- Scombroid
- Cold urticaria
- Contrast induced allergic reaction
- Shock
- Transfusion reaction
- Carcinoid syndrome
Evaluation
- Clinical
- Rule out Anaphylaxis
- Difficult to differentiate from Angioedema
Management
- H1 antagonist: Diphenhydramine 50mg IV/IM/PO
- H1 antagonists with low sedating activity, such as fexofenadine, loratadine, cetirizine, are preferred over diphenhydramine and hydroxyzine when appropriate[1]
- H2 antagonist: Famotidine 40mg OR ranitidine 150mg IV/IM/PO
- Improves urticaria but not angioedema at 2 hours[2]
- Consider corticosteroid: methylprednisolone 125mg IV/IM OR prednisone 60mg PO
- Continue steroid burst if outpatient (40mg prednisone PO x 5 days)
Disposition
- Consider brief observation in the ED for improvement of symptoms
See Also
References
- ↑ [Guideline] Zuberbier T, Asero R, Bindslev-Jensen C, Walter Canonica G, Church MK, Giménez-Arnau AM, et al. EAACI/GA(2)LEN/EDF/WAO guideline: management of urticaria. Allergy. 2009 Oct. 64(10):1427-43
- ↑ Lin, RY et al. Improved Outcomes in Patients With Acute Allergic Syndromes Who Are Treated With Combined H1 and H2 Antagonists. Annals of Emergency Medicine. 36:5 NOVEMBER 2000.
