From the Research
For an allergic rash to amoxicillin in a child under 2 years old, diphenhydramine (Benadryl) is typically recommended at a dose of 1.25mg/kg every 6 hours as needed. This recommendation is based on the most recent and highest quality study available, which emphasizes the importance of proper management of antibiotic allergy in children 1. The dose of diphenhydramine can be calculated based on the child's weight, with a typical 1-year-old weighing about 10kg requiring about 12.5mg per dose. Liquid formulations are available, usually 12.5mg/5mL.
The rash should improve within 1-3 days, though it may take up to 2 weeks to completely resolve. It is essential to stop the amoxicillin immediately and contact the child's healthcare provider, as they may need to prescribe an alternative antibiotic if the child was taking amoxicillin for an infection. Cool baths and loose cotton clothing can help soothe the skin, and applying a gentle, fragrance-free moisturizer after bathing can also be beneficial. If the child develops difficulty breathing, swelling of the face or lips, or seems very ill, seeking emergency care immediately is crucial, as these could indicate a more severe allergic reaction.
Diphenhydramine works by blocking histamine receptors, reducing the allergic response that causes the rash, as discussed in the context of antihistamine use in children 2. Documenting this reaction is vital, as the child will need to avoid amoxicillin and related antibiotics in the future. The management of antibiotic allergy in children requires a practical approach, including confirmation of the diagnosis and finding a safe alternative to the culprit antibiotic 1.
Key considerations in managing pediatric patients with antibiotic hypersensitivity reactions include:
- Confirming the diagnosis and identifying a safe alternative antibiotic
- Using skin tests or challenge tests for diagnosis when necessary
- Avoiding "labeling" a child as allergic without a proper diagnostic workup
- Considering the use of antihistamines like diphenhydramine for symptomatic relief, as supported by studies on antihistamine use in children 2 and the management of antibiotic allergy 1.