Harlequin color change (HCC) of the newborn, or harlequin phenomenon, is a transient unilateral erythema that is seen in up to 10% of healthy newborns. HCC is macular and blanchable, and displays a sharp midline cutoff. It is often gravity dependent. HCC typically presents between 2 and 5 days of life, with some infants presenting with episodes up to the third week. The exact etiology of HCC is unknown, but current evidence points to sympathetic autonomic dysfunction in the control of capillary tone, likely secondary to hypothalamic immaturity in the newborn.

Most cases are idiopathic in healthy neonates. HCC has also been noted in the setting of prematurity, low birth weight, hypoxia, infusion of prostaglandin E1 (PGE1), and neonatal meningitis. 

The transient color change lasts anywhere from 30 seconds to 20 minutes and recurs up to 12 times over a period of 24 hours. Of note, typical HCC occurs without changes in vital signs, pain, or other signs or symptoms. Hemiscrotal- and hemifacial-limited variants as well as a patchy erythema variant have been reported.