In a pediatric patient with a mild allergic reaction, what is the Benadryl dosing?

• A. 0.5 mg/kg IV/IO
• B. 0.5 mg/kg IM
• C. 1 mg/kg IV/IO (Diluted) or IM (Max total 50 mg)
• D. 2 mg/kg IM

Answer: (C)

Weight-based dosing is the key. For a pediatric patient with a mild allergic reaction, diphenhydramine is given as 1 mg per kilogram of body weight per dose, with a maximum of 50 mg per dose. This dose can be administered intramuscularly or, if giving it IV/IO, it must be diluted (to reduce irritation and adverse effects from a concentrated bolus). The 1 mg/kg dose is correct because it provides enough antihistamine effect to help relieve itching, hives, and swelling without exceeding safety limits. A smaller dose like 0.5 mg/kg may be less effective, while a dose of 2 mg/kg would exceed the safe per-dose maximum and increase the risk of sedation and anticholinergic side effects.