Acute allergic reaction: Difference between revisions

(Text replacement - "==Diagnosis==" to "==Evaluation==")
(Add MedicationDose entries (diphenhydramine, cetirizine, famotidine, methylprednisolone, prednisone) with SMW annotations)
 
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==Management==
==Management==
#[[H1 antagonist]]: [[Diphenhydramine]] 50mg IV/IM/PO
#[[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<ref>[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</ref>
#*H1 antagonists with low sedating activity, such as fexofenadine, loratadine, cetirizine, are preferred over [[diphenhydramine]] and hydroxyzine when appropriate<ref>[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</ref>
#[[H2 antagonist]]: [[Famotidine]] 40mg OR [[ranitidine]] 150mg IV/IM/PO
#**[[Cetirizine]] 10mg IV/PO (6-11 years old: 5-10 mg IV; 6 mo - 5 years: 2.5 mg IV)
#[[H2 antagonist]]: [[Famotidine]] 40mg '''OR''' [[ranitidine]] 150mg IV/IM/PO
#*Improves urticaria but not angioedema at 2 hours<ref>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.</ref>
#*Improves urticaria but not angioedema at 2 hours<ref>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.</ref>
#Consider [[corticosteroid]]: [[methylprednisolone]] 125mg IV/IM OR [[prednisone]] 60mg PO
#Consider [[corticosteroid]]: [[methylprednisolone]] 125mg IV/IM '''OR''' [[prednisone]] 60mg PO
#*Continue steroid burst if outpatient (40mg [[prednisone]] PO x 5 days)
#*Continue steroid burst if outpatient (40mg [[prednisone]] PO x 5 days)
==Medication Dosing==
{{MedicationDose
| drug = Diphenhydramine
| dose = 50mg
| route = IV/IM/PO
| context = H1 antagonist
| indication = Acute allergic reaction
| population = Adult
}}
{{MedicationDose
| drug = Cetirizine
| dose = 10mg
| route = IV/PO
| context = H1 antagonist; less sedating alternative
| indication = Acute allergic reaction
| population = Adult
}}
{{MedicationDose
| drug = Cetirizine
| dose = 5-10mg IV (6-11yo); 2.5mg IV (6mo-5yo)
| route = IV
| context = H1 antagonist; less sedating alternative
| indication = Acute allergic reaction
| population = Pediatric
}}
{{MedicationDose
| drug = Famotidine
| dose = 40mg
| route = IV/IM/PO
| context = H2 antagonist; improves urticaria
| indication = Acute allergic reaction
| population = Adult
}}
{{MedicationDose
| drug = Methylprednisolone
| dose = 125mg
| route = IV/IM
| context = Corticosteroid
| indication = Acute allergic reaction
| population = Adult
}}
{{MedicationDose
| drug = Prednisone
| dose = 60mg initially, then 40mg PO daily x 5 days
| route = PO
| context = Corticosteroid (outpatient)
| indication = Acute allergic reaction
| population = Adult
}}


==Disposition==
==Disposition==
*Consider brief observation in the ED for improvement of symptoms
*Consider brief observation in the ED for improvement of symptoms
*Send home with an [[anaphylaxis]] emergency plan and [[epinephrine]] autoinjector! (Epi-Pen)


==See Also==
==See Also==
*[[Anaphylaxis]]
*[[Anaphylaxis]]
*[[Chronic urticaria]]


==References==
==References==

Latest revision as of 18:25, 20 March 2026

Background

Clinical Features

Raised urticaria
  • Presentation can be delayed

Differential Diagnosis

Acute allergic reaction

Evaluation

Management

  1. 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]
      • Cetirizine 10mg IV/PO (6-11 years old: 5-10 mg IV; 6 mo - 5 years: 2.5 mg IV)
  2. H2 antagonist: Famotidine 40mg OR ranitidine 150mg IV/IM/PO
    • Improves urticaria but not angioedema at 2 hours[2]
  3. Consider corticosteroid: methylprednisolone 125mg IV/IM OR prednisone 60mg PO
    • Continue steroid burst if outpatient (40mg prednisone PO x 5 days)


Medication Dosing

Diphenhydramine 50mg IV/IM/PO Cetirizine 10mg IV/PO Cetirizine 5-10mg IV (6-11yo); 2.5mg IV (6mo-5yo) IV Famotidine 40mg IV/IM/PO Methylprednisolone 125mg IV/IM Prednisone 60mg initially, then 40mg PO daily x 5 days PO

Disposition

  • Consider brief observation in the ED for improvement of symptoms
  • Send home with an anaphylaxis emergency plan and epinephrine autoinjector! (Epi-Pen)

See Also

References

  1. ↑ [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
  2. ↑ 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.
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