Vernix: Definition, Biology, Function, Structure, Composition and Benefits for the Baby

This coating develops on the baby’s skin while it is in the womb.

Vernix caseosa is a protective layer on the baby’s skin. It appears as a white, cheese-like substance. Traces of the substance can appear on the skin after birth. You may wonder, what is the purpose of this coating?

The name vernix caseosa has its origin in the Latin terms vernix, which means ‘varnish’, and caseoso, which means ‘cheese’, which gives an idea of ​​the appearance that this unctuous layer offers, which accumulates especially on the back, the scalp and the folds of the extremities of the newborn.

Vernix caseosa biology

According to current knowledge, vernix production is unique to humans.

As early as 3 weeks gestation, it consists of a single layer of cuboidal cells developed from the embryonic ectoderm and by the 11th week, the epidermis has three distinctive layers: basal, intermediate, and superficial (peridermis).

The peridermis provides a suitable temporary barrier to the aqueous environment in the uterus with an active transport mechanism between the amniotic fluid and the embryo by virtue of its microvilli on its apical surface.

The durable cytoskeletal framework of the keratin macro fibrils and cornified envelope is formed to provide “brick and mortar” like mechanical strength.

Peridermal cells are continually replaced until 21 weeks when they are completely shed and replaced by the stratum corneum.

The shed peridermal cells mix with the sebum secretions of the sebaceous glands within the epithelial walls.

It is within this combination that the formation of vernix caseosa occurs.

Structure and composition of vernix caseosa

Vernix consists of water (81%), lipids (9%), and proteins (10%).

The vernix exhibits a non-lamellar lipid matrix containing hydrated corneocytes without intercorneal desmosomal connections, in contrast to the adult stratum corneum, which contains mature corneocytes and lamellar lipid matrix.

Therefore, the structure of the vernix exhibits the morphology of “pasta and cheese” with a “mobile” architecture.

The specific composition of the material reflects cholesterol esters and wax esters, ceramides derived from the stratum corneum and squalene of sebaceous origin, cholesterol, triglycerides, free fatty acids, phospholipids and cellular elements.

Nonpolar lipids, such as sterol esters and triglycerides, predominate among free lipids and have a chain length of up to 32 carbon atoms.

The profile of the fatty acids, hydroxy acids and hydroxyceramides, which represent the bound lipids of vernix, shows a great similarity to that of the stratum corneum; however, vernix lipids show a lower degree of ordering compared to the stratum corneum.

Although about 80% of vernix is ​​water, it still has a high viscosity, suggesting that your water must reside in a highly structured state that hypothetically confers the abundance of water-filled fetal corneocytes on vernix.

These fetal corneocytes in the uterus act as ” cellular sponges ” to facilitate and maintain cornification by intercepting water moving through the fetus’s skin, while sebaceous lipids in the vernix provide a hydrophobic barrier.

Ultrastructural studies show hydrated corneocytes lacking nuclei and other organelles with a sparse network of keratin filaments, approximately 1-2 microns thick, without desmosomal connections, and surrounded by a thick layer of amorphous lipids without lamellae.

The intercellular lipid contains unidentified inclusion bodies, presumably protein material of keratinocytic origin or sebocyte debris.

Histochemistry shows variable acid phosphatase activity intracellularly or in amorphous lipid matrix.

Immunofluorescent staining tests of frozen VC smears show that only immunoglobulin G conjugate produces a strong positive reaction at antigen sites on VC cells.

Previous studies have shown that vernix possesses antimicrobial polypeptides. Recently, Maria Tollin et al performed an analysis of the vernix caseosa proteome and demonstrated the presence of potent antimicrobial polypeptides.

A total of 41 proteins have been detected, of which are novel for vernix. Indeed, 39% of the identified vernix proteins are components of innate immunity and 29% have direct antimicrobial properties.

The origin of vernix proteins appears to be multiple amniotic fluid, fetal lungs, blood contamination, dermal origins, activated keratinocytes.

Functions of the vernix caseosa

The vernix within the amniotic fluid when ingested by the fetus has potential effects on the developing intestine.

Glutamine that is> 20% of the amino acid content of vernix is ​​a known trophic factor for the developing intestine and is generally required by rapidly proliferating cells such as the intestinal epithelium and lymphocytes.

Asparinase is also found in abundance, making up> 30% of the amino acid content.

Vernix performs an epidermal barrier function in the uterus to facilitate epidermal growth underneath and acts as a hydrophobic barrier against amniotic fluid maceration and fluid and electrolyte loss or TEWL (trans epidermal water loss).

Vernix also acts as a protective biofilm by minimizing friction of the fetal parts during delivery and as an antimicrobial covering against the bacteriologically rich environment of the mother’s genital tract along with the isolating effect on the fetus.

Vernix caseosa benefits

In the last few years of practice, as soon as your baby came out of your womb, they took him to his first bath, had the substance removed, and had a series of tests done.

Fortunately, research has shown that delaying your baby’s first bath and allowing vernix to reside on the skin has several health benefits:

Has antimicrobial properties

Recent studies have shown that vernix contains antimicrobial amino acids that block invading bacteria present in amniotic fluid from meconium contamination.

After your baby is born, these amino acids work to protect against harmful bacteria like B. streptococcus and E. coli.

Vernix has wound healing properties

Vernix has been shown to help with rapid skin regeneration after injury. In fact, the use of vernix on the skin that grafts the burned areas of burn victims is being investigated.

Moisturize your baby’s skin

Your baby’s skin undergoes an immediate change after birth, including dehydration. Due to its high water content, vernix acts as a natural moisturizer for your baby, protecting their skin from dryness and cracking.

As the move toward evidence-based practice has become standard, more hospitals are delaying a baby’s first bath between 24 and 48 hours after delivery.

However, many families choose to wait several days or even up to a week after the birth. How long you choose to delay the bath is entirely up to you.

If you decide to wait to give your baby the first bath, you can gently massage the coating onto your baby’s skin for the next few days.

So after giving birth to your baby, don’t be surprised if they came with a thick layer of vernix – it’s there for a reason! Instead, take advantage of that moment to snuggle up with your baby and enjoy the skin-to-skin magic.

Retention of vernix in newborn skin care

Traditional practice has directed nurses to clean the vernix caseosa from the moist skin of the newborn as part of the initial care in the birthing center.

As thermoregulation and resuscitation are the priorities of care, cleansing the skin was considered the preferred method to achieve drying and stimulation of respiratory effort.

As the movement toward evidence-based practice has become a major practice effort and the procedure for this nursing activity has come under scrutiny.

In 1998, the National Association for Neonatal Nursing (NANN) and the Association of Obstetric and Neonatal Nursing for Women’s Health (AWHONN) conducted a national multi-site study.

A consensus statement based on the results of the study directed “removal of all vernix is ​​not necessary for hygiene reasons” and “vernix may provide antibacterial promotion and wound healing”.

Interestingly, the World Health Organization (WHO) also recommends leaving the vernix intact on the skin’s surface after birth.


Vernix caseosa is a white, creamy and natural biofilm that covers the skin of the fetus during the last trimester of pregnancy.

The vernix coating on the neonatal skin protects the newborn’s skin and facilitates the extrauterine adaptation of the skin in the first postnatal week if it is not washed after birth.

It consists of water-containing corneocytes embedded in a lipid matrix.

The strategic location of the vernix on the surface of the fetal skin suggests participation in multiple overlapping functions required at birth, such as the barrier to water loss, temperature regulation, and innate immunity.

The vernix appears to play several integral roles during the fetus’s transition from intrauterine to extrauterine life.