Vernix caseosa

Traces of vernix caseosa on a full term newborn.

Vernix on a newborn's feet.

Vernix caseosa, also known as vernix, is the waxy or cheese-like white substance found coating the skin of newborn human babies.

Composition

Vernix has a highly variable makeup but is primarily composed of sebum, cells that have sloughed off the fetus's skin and shed lanugo hair. 12% of the dry weight of vernix is branched-chain fatty acid-containing lipids, cholesterol and ceramide. Vernix of term infants has more squalene and a higher wax ester to sterol ester ratio than preterm infants.

Function

Vernix is theorized to serve several purposes, including moisturizing the infant's skin, and facilitating passage through the birth canal. It serves to conserve heat and protect the delicate newborn skin from environmental stress. Vernix is also thought to have an antibacterial effect; though there is little to support a chemical role of vernix in protecting the infant from infection, it may form a physical barrier to the passage of bacteria.

Newborn baby with vernix on parts of her skin

Secretion

The sebum in vernix is produced in utero by the sebaceous glands around the 20th week of gestation. Vernix appears primarily in full term infants, while premature and postmature births generally lack any. Postdates desquamation (flakey skin in babies born >42 weeks) is thought to be due to loss of vernix.

Etymology

In Latin vernix means varnish and caseosa means cheesy.