Recharacterization of the Nonlesional Dry Skin in Atopic Dermatitis through Disrupted Barrier Function

Background: The etiology of the nonlesional dry and barrier-disrupted skin of patients with atopic dermatitis (AD) is still unclear. Objective: To determine whether disrupted barrier function in the nonlesional skin is associated with inflammatory or postinflammatory events, which are relevant to the severity of AD or local dry skin properties, respectively. Methods: We evaluated the barrier function and the water content of nonlesional forearm skin and compared these with the severity of AD and the intensity of dryness/scaling/itchiness at the same skin sites. Results: The transepidermal water loss (TEWL) significantly increased in proportion to the severity of AD with a markedly high correlation coefficient (r = 0.834, p < 0.0001, n = 106), while the capacitance decreased in proportion to the severity of AD with a relatively lower correlation coefficient (r = –0.720, p < 0.0001, n = 106) compared with TEWL. Relationship between TEWL and capacitance values in association with the AD severity revealed that the two parameters are well distributed, corresponding to the severity of AD, and that the elevated TEWL more adequately reflects the difference between healthy control and the mild group of AD compared with the reduced capacitance. Comparison with dry skin properties revealed that while the capacitance values were highly correlated with dryness (r = –0.752, p < 0.0001, n = 106) and with scaling (r = –0.697, p < 0.0001, n = 106), the TEWL was also related to dryness (r = 0.788, p < 0.0001, n = 106) with a higher correlation coefficient compared with capacitance and to scaling (r = 0.697, p < 0.0001, n = 106). Conclusion: Our results indicate that the barrier disruption in the nonlesional skin is well suited to reflect the severity of AD as well as the dry skin properties, providing a useful insight into understandings of diagnosis and clinical improvement during therapy.