Since ETN rarely is seen in premature infants, it is believed that mature newborn skin is required to produce this reaction pattern. Although 1 study found that infants with ETN had an increased risk of atopy, subsequent studies have failed to support this finding. No racial or ethnic predisposition is known. Males and females are affected equally. Rare cases have been reported at birth.
Incidence rises with increasing gestational age and birth weight.
Delayed onset rarely may occur in full-term and preterm infants up to age 14 days. Infants with ETN otherwise are healthy and lack systemic symptoms. Recurrences are uncommon but have been reported up to the sixth week of life. They tend to be mild in severity. Focus the physical examination on location, size, and distribution of macules, wheals, papules, and pustules on the skin.