Sebaceous hyperplasia in newborns is a transient condition, influenced by androgens, and it represents localized hypertrophy of sebaceous glands on the face. It is most prominent around the nose and upper lip, where the density of sebaceous glands is highest. In the newborn, circulating maternal hormones can stimulate sebaceous gland growth and activity leading to sebaceous hyperplasia. Sebaceous hyperplasia owes its appearance to enlarged mature sebocytes and increased sebaceous gland acini.

Sebaceous hyperplasia occurs in nearly half of term newborns with premature infants being less commonly affected.