Treatment of Diffuse Hives with Erythema Multiforme in Children

Critical Safety Issues

The American Academy of Pediatrics recommends avoiding diphenhydramine in children under 6 years of age due to significant safety concerns, with 33 deaths associated with its use in children under 6 years between 1969-2006, and 41 deaths in children under 2 years 1
The FDA and pediatric advisory committees explicitly recommend against using over-the-counter cough and cold medications, including first-generation antihistamines like diphenhydramine, in children below 6 years of age 1

The American Academy of Pediatrics recommends replacing diphenhydramine with cetirizine 2.5 mg twice daily (approved for ages 2-5 years) as the safer antihistamine option 1
Alternatively, loratadine 5 mg once daily can be used for children aged 2-5 years, with superior safety profiles and low rates of serious adverse events 1
The British Medical Association suggests that second-generation antihistamines have very low rates of serious adverse events in young children and lack the sedating effects of first-generation agents 1

The British Medical Journal recommends assessing response to treatment within 24-48 hours; if no improvement or continued worsening, urgent referral to pediatric dermatology or allergy is indicated 2
Failure to respond to first-line management (topical measures and antihistamines) is an explicit indication for specialist referral, according to the British Medical Journal 2

The British Medical Journal states that antihistamines alone have limited efficacy when symptoms are progressive and severe, as their therapeutic value resides principally in sedative properties for pruritus rather than treating the underlying inflammatory process 3, 2
The worsening course over 3 days despite antihistamine therapy indicates a more aggressive inflammatory process requiring systemic anti-inflammatory treatment, according to the British Medical Journal 2
Systemic corticosteroids have a definite role in severe acute urticarial/erythema multiforme presentations in children when first-line measures fail, as recommended by the British Medical Journal 2

The British Medical Journal advises not to use systemic corticosteroids as maintenance therapy; they are appropriate only for short-term control of acute flares 2
Monitor for secondary bacterial infection, which would require antibiotics (flucloxacillin for S. aureus or erythromycin if penicillin allergy), as recommended by the British Medical Journal 3, 2
If fever develops or the child appears systemically unwell, consider eczema herpeticum (requires oral acyclovir) or other serious complications requiring immediate medical evaluation, according to the British Medical Journal 3, 2
Liquid formulations of medications are preferred in young children for easier administration and better absorption, as recommended by the American Academy of Pediatrics 1

Antihistamines show only 42-65% good or very good response rates even in optimal conditions, and their value may be progressively reduced due to tachyphylaxis, according to the British Journal of Dermatology 4, 2
Non-sedating antihistamines have little value in severe inflammatory skin conditions beyond symptomatic pruritus relief, as stated by the British Medical Journal 3, 2
The 3-day failure to respond with worsening symptoms indicates the need for escalation rather than continuation of ineffective therapy, according to the British Medical Journal 2