Ultrastructural studies have shown that the epidermis of full-term infants born after 40 weeks of gestation is morphologically indistinguishable from that of adults. It was therefore assumed that the biophysical properties are similar as well (Yosipovitch 2000).
The present study investigated skin physiology in neonates, especially the barrier function during the first 4 weeks of life and the influence of bathing and washing.
The following important results could be obtained: significant differences in skin barrier function were shown to be dependent on postnatal age, gender and anatomical region. In addition, a beneficial effect of bathing twice weekly with clear water compared to washing with tap water on neonatal skin during the first four weeks of life was evident.
Thus, the anatomical and morphological appearance of full-term newborn skin correlates with the functional maturation only partly. This discrepancy affects the skin barrier function located in the outermost layer of the epidermis, in the SC.
The values of skin physiological parameters in healthy full-term newborns infants obtained in this study differ from adult values cited in the literature (Pinnagoda 1990, Hoeger and Enzmann 2002) and in product information (Courage und Khazaka 2002). The results of the present study showed that a healthy full-term newborn infant has lower SCH (19.3-35.3 vs. >60 units) and sebum (<50 vs. 100-220 µg/cm2), and higher pH (up to 6.2 vs. 4.5-5.5 units) on day 2after birth.
Interestingly, already on day 2, values of TEWL are comparable to adults (<10g/m2/h).
Normally, the functional maturation of the SC begins in the third trimester, at around 24 weeks (Holbrook 2000), whereas, the skin barrier of preterm newborns matures only during the first 10-14 postnatal days, whilst in preterm newborns born before 23 weeks of gestation this process can last up until 8 weeks. However, the adaptation process of skin barrier to extrauterine life in full-term newborns is not completely understood. Thus, the aims of this study were to prospectively monitor the changes in different skin parameters, determine when the SC matures and reaches full barrier function and to investigate the effect of bathing with clear water on skin barrier during the first four weeks of life.
57 healthy, full-term newborns (32 boys and 25 girls) aged less than 48 hours were randomly assigned to 2 groups: “b” (bath) and “w” (wash). Group “b” (n=29) received a bath twice weekly with clear water and group “w” (n=28) was washed with a wet cotton wool cloth twice weekly, starting after the 7th day of life in both groups. TEWL, skin pH, sebum production and SCH were measured at day 2, day 7 and day 28 under standardized conditions on the forehead, abdomen,
upper leg and buttock using a non-invasive Multi Probe Adapter System MPA® connected with four probes: tewameter, corneometer, pH-meter and sebumeter.
The statistical analysis of the results obtained in both groups showed a significant increase in SCH and sebum as well as a significant decrease in pH values during the first four weeks of life.
These findings indicate that in healthy full-term newborn infants, directly after birth, cutaneous adaptation or maturation process takes place and is not completely finished at the end of the fourth week.
The time needed for normalization of skin parameters depends on the different skin physiological parameters (TEWL, SCH, pH and sebum). Up until day 7, sebum and up until day 28 pH reached values comparable to those in older children and adults. In contrast, SCH did not reach the standard values obtained in adults even at the end of the fourth week. Interestingly, during the whole study period TEWL was remarkably stable, confirming previous findings that the adaptation process for TEWL only takes place during the first four postnatal hours.
It seems that all skin physiological parameters, such as TEWL, SCH, pH and sebum should be used as a marker to evaluate the adaptation process of skin to extrauterine life in healthy full-term newborn infants. So far, TEWL was the main parameter used for evaluation of skin barrier effectiveness, perhaps because of the marked differences in TEWL between pre- and full-term newborns and physiological and pathological skin conditions. Until now, TEWL has been a highly important parameter for the evaluation of skin barrier in pathological states, but it is also a parameter which needs highly standardized measurement conditions in order to provide reliable and reproducible results.
Comparing parameters between genders, significantly higher transepidermal water loss and higher hydration of SC was found for the first time on the buttock in females. The present study also proved that the differentiation process of pH between full-term newborn females and males begins on day 7 after birth and lasts at least until day 28.
Among all four anatomical regions measured in the present study, the values of skin parameters deviated mostly on the buttock by contrast with other anatomical regions. This study confirms the assumption that the buttock is the most sensitive region in a newborn, so special skin care in this region is recommended. However, the exact type and schedule of skin care should be confirmed in further research studies.
This is the first study comparing skin function parameters between healthy term newborns investigating on the one hand, the stratum corneum maturation and on the other hand, the influence of washing and bathing. The study results demonstrated that bathing with clear water
leads to a better skin barrier function than washing a newborn: specifically, a lower transepidermal water loss on the buttock and a higher hydration of the stratum corneum on the forehead and abdomen were noticed. Moreover, healthy full-term newborn infants can be bathed with clear water from the 7th day of life without negative influence on the newborn’s general condition and skin adaptation process.