Vernix caseosa

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For the town in France, see Vernix, Manche.

Large amounts of vernix on babies feet, baby not yet rubbed down, baby approximately 60 seconds out of womb.

Traces of vernix caseosa on a full term newborn

Vernix, also known as Vernix caseosa, is the waxy or "cheesy" white substance found coating the skin of newborn humans. It is secreted by the fetus's sebaceous glands in utero, and is hypothesized to have antibacterial properties. Vernix is the Latin word for "varnish." The vernix (or "varnish"), "varnishes" the baby. Caseosa is "cheesy" in Latin

Vernix is composed of sebum (the oil of the skin) and cells that have sloughed off the fetus' skin.

The vernix is secreted by the sebaceous glands around the 20th week of gestation, presumably to protect the baby's skin from dehydration in the womb. Without the vernix, the baby would have very wrinkled skin from constant exposure to the watery amniotic fluid. The amount of vernix present decreases toward the end of gestation.

Vernix is sometimes offered as supporting evidence for the Aquatic Ape Hypothesis (AAH/AAT) that the reason for the divergence between the hominids and their ape-like relatives was due to a long semi-aquatic phase of history. No other land mammal, including the apes, produces vernix-coated neonates; in contrast, some sea mammals, including the harbour seal, do (Prog. 2 of BBC series on AAH/AAT quoting Professor Don Bowen of Nova Scotia's Department of Fisheries and Oceans Marine Mammal Division.).