New insight on barrier function development in infant skin

Key Points

Skillman, N.J. - Findings from studies of infant skin challenge existing beliefs about maturation of skin barrier function and are expected to provide useful insight for developing optimal skincare products for babies, say researchers from Johnson & Johnson Consumer and Personal Products Worldwide.

Janet Nikolovski, Ph.D., and colleagues reported the pooled results from a series of five studies that used standard and novel laboratory instrumentation to investigate the barrier function in infant and adult skin. The results showed there were significant differences between the two populations and also demonstrated that the barrier function of infant skin continued to change throughout the first year of life.

"There are clearly appreciable differences in the quality and appearance of adult and infant skin. However, a search of the literature identified ... few studies on the development of healthy baby skin," notes Dr. Nikolovski, principal scientist, Advanced Technologies, Johnson & Johnson Consumer and Personal Products Worldwide, Skillman, N.J.

According to Dr. Nikolovski, "Our findings reaffirm there are differences between adult and infant skin, but challenge current concepts that skin barrier function reaches maturation by the 34^th week of gestation.

"We are hypothesizing the barrier function and water-handling properties of the stratum corneum may remain in a state of flux during the first year of life, while more steady regulation mechanisms develop. We will be studying that now in greater detail, as we also try to identify structural correlates for the functional findings and collaborate with formulation scientists to understand how this information can be integrated into developing skincare products that take into account these newly identified, unique features and needs of infant skin," she tells Dermatology Times.

Study particulars

All the participants in these studies were Caucasian.

Data were analyzed from 124 full-term infants ages 3 months to 1 year. The testing was performed using standard instrumentation for measuring transepidermal water loss (TEWL) and skin conductance, but also used Raman confocal microspectroscopy for in vivo analysis of water content in skin at varying depths throughout the upper 40-micron layer. In addition, dynamic water handling was investigated that tracked water absorption and evaporation/dissipation after skin surface exposure.

Overall, the various measurements confirmed previous reports that the water content is higher in infant skin compared with adult skin. However, the researchers also found that skin conductance and TEWL values decreased with increasing infant age. In addition, the variance in those data was much greater within the infant cohort compared with the adults, but the inter-infant variability also seemed to decrease with increasing infant age.

"We ... speculate that it may reflect differences in rates of skin development among the infants or different histories of exposure to environmental factors," Dr. Nikolovski says.

Water content

The Raman confocal microspectroscopy studies confirmed the higher water content in infant skin relative to adults and showed the differences were maintained at various depths through at least the upper epidermis.

Further analysis showed there was a steeper water gradient in infant skin with a higher mass concentration of water in the stratum corneum.

"Water content in the stratum corneum affects maturation of that layer because it influences the activity of enzymes involved in differentiation. Therefore, we believe these findings have biologic relevance as they can shed light on the process of stratum corneum differentiation in infant skin," Dr. Nikolovski says.

When a drop of water was placed on the skin surface for 15 seconds and then blotted off, serial skin conductance measurements showed infant skin absorbed the water at a significantly faster rate relative to the adults, but also lost hydration significantly faster. Further analyses showed that process occurred with a single time constant of 30 seconds in the adults. However, water desorption in the infant skin followed two processes - the first had a time constant of 12 seconds and the second had a time constant similar to that observed in the adults.

"One possible explanation for these findings is stratum corneum differences account for more rapid desorption in infant skin, whereas in deeper layers, the process may be more similar regardless of age," Dr. Nikolovski says.

In another experiment, the skin was exposed for 10 seconds to a paper towel saturated with water. Use of Raman confocal microspectroscopy to track water movement through the skin showed no increase in hydration of adult skin, whereas there was significant water uptake within the upper 10 microns of the infant skin.

"This supports the notion that infant skin absorbs water more readily within the stratum corneum," she says.