Vernix caseosa, also known as vernix, is the waxy or cheese

Cheese

Cheese is a generic term for a diverse group of milk-based food products. Cheese is produced throughout the world in wide-ranging flavors, textures, and forms....

-like white substance found coating the skin

Skin

-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...

 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

Lanugo

Lanugo is fine, downy hair as a type of fur. It is often found in teratomas .-Fetal development:Lanugo grows on fetuses as a normal part of gestation, but is usually shed and replaced by vellus hair at about 33 to 36 weeks of gestational age...

 hair. 12% of the dry weight of vernix is branched

Branching (chemistry)

In polymer chemistry, branching occurs by the replacement of a substituent, e.g., a hydrogen atom, on a monomer subunit, by another covalently bonded chain of that polymer; or, in the case of a graft copolymer, by a chain of another type...

-chain fatty acid

Fatty acid

In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...

-containing lipids, cholesterol

Cholesterol

Cholesterol is a complex isoprenoid. Specifically, it is a waxy steroid of fat that is produced in the liver or intestines. It is used to produce hormones and cell membranes and is transported in the blood plasma of all mammals. It is an essential structural component of mammalian cell membranes...

 and ceramide

Ceramide

Ceramides are a family of lipid molecules. A ceramide is composed of sphingosine and a fatty acid. Ceramides are found in high concentrations within the cell membrane of cells. They are one of the component lipids that make up sphingomyelin, one of the major lipids in the lipid bilayer...

. Vernix of term infants has more squalene

Squalene

Squalene is a natural organic compound originally obtained for commercial purposes primarily from shark liver oil, though plant sources are used as well, including amaranth seed, rice bran, wheat germ, and olives. All plants and animals produce squalene, including humans...

 and a higher wax ester

Wax ester

An ester of a fatty acid and a long-chain alcohol. These oils have similar properties as triglycerides, but are indigestible. They are found in some fish such as orange roughy, oilfish, escolar, black oreo, smooth oreo and other deep water fish. They are also present in marine copepods. Wax...

 to sterol ester

Sterol ester

Sterol esters are a heterogeneous group of chemical compounds. They are created when the hydroxyl group of a sterol and a fatty acid undergo an esterification reaction. They can be found in trace amounts in every cell type but are highly enriched in foam cells....

 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

Vagina

The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

. 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.

Secretion

The sebum in vernix is produced in utero

In utero

In utero is a Latin term literally meaning "in the womb". In biology, the phrase describes the state of an embryo or fetus. In legal contexts, the phrase is used to refer to unborn children. Under common law, unborn children are still considered to exist for property transfer purposes.-See also:*...

 by the sebaceous gland

Sebaceous gland

The sebaceous glands are microscopic glands in the skin that secrete an oily/waxy matter, called sebum, to lubricate and waterproof the skin and hair of mammals...

s around the 20th week of gestation

Gestation

Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....

. 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.