Allergies | Pediatrics | OnlineMedEd

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Watch the whole lesson at When discussing allergies, we’re generally referring to IgE-mediated type 1 hypersensitivity. This will be basis of the majority of the conditions covered. For review, the full gamut of hypersensitivity reactions is briefly stated to the right.

Acute Allergic Presentations
Anaphylaxis
The dreaded complication of IgE-mediated allergic reactions, this can be life-threatening. It can involve multiple organ systems including: cardiovascular (hypotension), gastrointestinal (diarrhea), skin (hives), and pulmonary (airway edema). Anaphylaxis requires involvement of at least two organ systems; it doesn’t need to involve the airway. A confirmed exposure to an allergen isn’t always needed. Treat with epinephrine (1:1,000 IM), support the airway with intubation, and blood pressure with IV fluids and pressors if needed. Adjunctive therapy includes H1/H2 blockers and albuterol - they have more supporting evidence than steroids. Provide an epinephrine pen at discharge and advise staying away from allergic triggers.

Urticaria
This is the skin manifestation of allergic reactions. It’s usually IgE-mediated (type 1 hypersensitivity) but can also come from agents that cause non-immunologic mast cell degranulation (contrast, opiates, Red man syndrome from vancomycin). The skin will have erythema and wheals which are often pruritic and limited to superficial layers of dermis. Always check for signs/symptoms of anaphylaxis (dyspnea, wheezing, GI symptoms, etc.). To treat, use 2nd generation H1 antihistamines (cetirizine, loratadine, fexofenadine) and remove/avoid the offending agent (if possible). 1st generation H1 antihistamines can be used but have the side effect of sedation. Additional therapies such as H2 blockers, leukotriene antagonists, and steroids have a limited role; they’re typically reserved for more chronic causes of urticaria.

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