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Vernix Caseosa: The Ultimate Natural Cosmetic?
By: Johann W. Wiechers, PhD, JW Solutions; and Bernard Gabard, PhD, Iderma
Posted: August 31, 2009, from the September 2009 issue of Cosmetics & Toiletries.
- Figure 1. Vernix caseosa covers newborn infants
- Figure 2. Lipid, free lipid extract and ceramide analyses
- Figure 3. Water loss profiles
- Figure 4. Water loss profiles of vernix caseosa films as a function of relative humidity
- Figure 5. Equilibrium water sorption-desorption curves
- Figure 6. Percent barrier recovery after tape stripping versus film permeability
- Figure 7. Moisture accumulation assessment
- Figure 8. Water release profiles
- Figure 9. Microgels and coating lipids
- Figure 10. Water release profiles of native VC and various biofilms
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Vernix caseosa released water at roughly the same rate as the w/o emulsion. At the end of 3 hr, vernix caseosa and the water-in-oil emulsion lost 8.1% and 6.6% of their original water content, respectively.26 In contrast, the o/w emulsion released as much as 30% of its total water content within the first 30 min of the experiment and 81% by the end of the experiment.25
The water release rate depends on the thickness of the layer of vernix caseosa applied. Gunt showed that the percentage of water lost from vernix caseosa films decreases with an increase in film thickness.25 In addition, the water loss profile depends on the relative humidity of the external environment—at a higher relative humidity, more water is retained within vernix caseosa, yet the difference in water loss in the range of 82% to 98% relative humidity is dramatic, relative to the losses measured in the range of 35% to 82% relative humidity (see Figure 4).
Tansirikongkol et al. took this experiment one step further and measured sorption-desorption curves at different relative humidities. They assessed the equilibrium water content in native vernix caseosa and vernix corneocytes and compared this to the SC.27 The equilibrium water content for native vernix and vernix corneocytes decreased with decreasing water activity (desorption study) and increased with increasing water activity (sorption study). Native vernix caseosa released and absorbed water at a very low level at low relative humidities. Once the humidity reached approximately 90%, the sorption and desorption curves rose dramatically (see Figure 5a).
Similarly, the sorption and desorption of water in vernix caseosa corneocytes occurred in low levels at low humidities. However, compared to native vernix, isolated vernix corneocytes exhibited unusually high water sorption at the 75% relative humidity condition, resulting in a 5- to 7-fold increase over the water content at 64% relative humidity (see Figure 5b).27
When this data is compared with similar curves established for SC by Kasting and Barai,29 it can be seen that native vernix caseosa showed the most similar water sorption profile to the profile of human SC. This combination of graphs suggests that when the relative humidity is lowered, as happens during delivery, water is released from the vernix corneocytes into the vernix and therefore to the SC. In doing so, it ensures that the imperfect SC of the newborn baby will have sufficient water for all its enzymes to function properly, so that a proper barrier can be formed.