Erythema Toxicum Neonatorum

Erythema toxicum neonatorum is a common, benign and self-limiting rash of newborns. It consists of blotchy red patches with small pale papules or pustules, and eosinophils are found in the lesions. It affects 30 to 70 percent of term infants and is rare in preterm infants under 34 weeks and in babies under 2.5 kg. Its importance lies in distinguishing it from pustular rashes caused by infection.

• Onset is usually 24 to 72 hours after birth (range birth to 2 weeks). Lesions come and go in crops over 5 to 7 days and clear by 2 weeks, without scarring.
• Cause is unknown. A local immune response to first colonisation of hair follicles by skin commensals is proposed.
• It is not infectious and is unrelated to hygiene, feeding or maternal illness.
• The infant is systemically well.

• Blotchy erythematous macules 1 to 3 cm across, each with a central 1 to 4 mm pale yellow or white papule or pustule (a "flea bitten" look), on the trunk, face, proximal limbs and buttocks. Palms and soles are spared because they have no hair follicles.
• The number varies from a few to hundreds, and lesions move location within hours.
• The infant is afebrile, feeding and behaving normally.
• Red flags: vesicles with erosions and crusting (herpes simplex); pustules with surrounding erythema plus fever or poor feeding (bacterial infection); pustules on palms and soles (scabies, candida, transient neonatal pustular melanosis); onset after 2 weeks; an unwell infant, hypothermia, respiratory distress; maternal genital herpes or fever; bullae; rash lasting beyond 2 weeks.

• Clinical diagnosis from the appearance, timing and well infant.
• If uncertain: Wright or Giemsa smear of pustule contents shows many eosinophils; Gram stain and culture of pustule contents for bacteria; potassium hydroxide preparation or culture for Candida; herpes simplex PCR on a vesicle swab.
• Blood count may show mild eosinophilia (up to 20 percent). No other tests are needed.
• Differentials: transient neonatal pustular melanosis (present at birth, pustules without erythema leaving pigmented macules), neonatal acne, miliaria, milia, neonatal cephalic pustulosis, staphylococcal pustulosis, herpes simplex, congenital candidiasis, infantile acropustulosis, incontinentia pigmenti, scabies.

• Reassure the parents that the rash is harmless and will clear in days to 2 weeks.
• No treatment is needed. Do not use topical steroids, antibiotics or antiseptics.
• Skincare: bathe gently in warm water, avoid squeezing or rubbing lesions, avoid oils, creams and perfumed products, dress in loose cotton.
• If the infant becomes unwell or lesions are vesicular or crusted, admit and investigate as infection: swabs and cultures, aciclovir 20 mg/kg intravenously every 8 hours if herpes is suspected, and intravenous flucloxacillin with gentamicin for suspected staphylococcal sepsis, doses according to the local neonatal schedule.
• No follow up is needed unless the rash persists beyond 2 weeks or the infant becomes unwell.