Abnormality of skin physiology Harlequin phenomenon 2017-05-18T00:38:26Z The Harlequin phenomenon consists of a sudden change in skin color, resulting in two different body colors, one on each half of the body. The Harlequin phenomenon (HF) is most common in the newborn and can be a generalized phenomenon or only involve a specific body area. The HF of the newborn is thought to be secondary to a relative hypothalamic control immaturity of the sympathetic peripheral vascular tonus, although it has also been described in other age groups, primarily located to the face and neck and mostly caused by a sympathetic disautonomy. While certainly peculiar, the HF is a benign event in the newborn.