To our knowledge, this is the first study to evaluate the temporary impact of early bathing on the skin barrier function in newborns and explore the potential association between bathing and AD development. Our results demonstrated a deterioration in the skin barrier function after early bath, including decreased underarm SCH as well as decreased facial and underarm humidity. In addition, via a 12-month follow-up questionnaire, we found that newborns bathed within 36 hours after birth having a prevalence of AD development 4 times higher than those without bath.
Early studies suggesting bathing, as early as 1 hour of age, is safe for full-term newborns only evaluated axillary or rectal temperature, arterial blood saturations, and other vital signs [22-25]. In these studies, scholars demonstrated axillary and rectal temperature, blood pressure, respiration rate, heart rate, and early neonatal complications do not alter after early bathing or do not differ between groups with and without bath [22-25]. However, recent studies evaluating skin barrier metrics show controversies. Lund et al. recruited 100 newborns and randomized them into two groups to receive their first bath with water or with water and a liquid baby cleanser . Both groups exhibited a significant decrease in the SCH after bath, while the TEWL and skin pH also altered . In this study, there was no difference for any related covariate in the mother or newborn between the bathed group and non-bathed group. Although we did not observe significant TEWL alterations, significant SCH and skin humidity reductions were observed in bath newborns. Previous studies have demonstrated defective skin barrier function, such as impaired skin hydration, enables and enhances penetration of environmental allergens into the skin, causing allergies, inflammations, and infections [27, 28]. Atopic skin disease, such as AD, has been proved to be associated with skin infection and allergy . Our results are consistent with previous literature. In this study, newborns bathed within 36 hours after birth had a prevalence of developing AD in 12-month 4-fold higher than those without bath, while there was not significant difference in related covariates, including the family history of allergies. This suggests the potential association between early bathing and AD development.
Therefore, a delayed bathing is suggested to maintain the skin barrier function in newborns. In one study, Bartels et al. recruited 57 healthy full-term newborns and demonstrated significant increases in the SCH at variant body regions from postnatal day-2 to day-7 by only washing newborns with a wet cotton washcloth twice weekly . This study also suggested if healthy full-term newborns received the first bathing after the 7th postnatal day, there would be no harm to the skin barrier function . Based on these evidences and findings in our current study, we suggest to dry and cover the newborn immediately after birth. Then, wash the newborn using a wet towel or cotton washcloth twice weekly for the first postnatal week, while delaying the first bathing to the second week after delivery.
Previous studies also demonstrated benefits of applying proper emollient in newborns to protect the integrity of the skin barrier function [31, 32]. Emollient can facilitate the SC to maintain proper hydration and decrease the TEWL [31, 33]. It can be used to treat post-bathing or post-washing skin changes including dryness, erythema, irritation, and other barrier alterations [34-36]. In addition, by maintain skin moisture, repairing or enhancing skin barrier, and reducing the need of anti-inflammatory measures, emollient also contributes in preventing or modifying the development of AD [37, 38]. Therefore, we recommend a routine emollient application in newborns, especially after bathing or washing.
In this study, we only evaluated temporary alterations in the skin barrier function after newborns taking the early bath. A future study is needed for evaluating a relatively long-term impact of bathing and monitoring the change of skin microbiota.
In conclusion, bathing a newborn within 36 hours after birth has a temporary negative impact on the SCH and skin humidity. We also found a positive correlation between early bathing and AD development. Deteriorated skin barrier function may leave the newborn susceptible to infection and allergy, increasing the risk of triggering AD onset.