Background: Atopic dermatitis (AD) can be considered a barrier disease in which antigens and irritants that can easily penetrate clinically normal, nonlesional skin due to its defective barrier function trigger and worsen the dermatitis. Thus, replenishing the barrier function in clinically normal, nonlesional skin of patients with AD seems to be a key for preventing the refractory nature of the dermatitis. Objective: To determine whether the disrupted barrier function of AD nonlesional skin can be repaired by topical application of a synthetic ceramide known to induce barrier recovery and to subsequently evaluate the relationship between enhanced barrier function and improved dry skin conditions. Methods: We applied topically a synthetic ceramide (CER) or hirudoid (HIRU)-containing cream to the nonlesional skin of AD patients for 4 weeks and evaluated their efficacy by measuring transepidermal water loss (TEWL) and capacitance values as well as clinical scoring for scaling/dryness/itchiness. Results: Treatment for 4 weeks with the CER cream significantly reduced dryness/scaling/itchiness which was accompanied by significant decreases in TEWL and increases in capacitance values at 2 and 4 weeks. In contrast, treatment for 4 weeks with the HIRU cream elicited a similar but lesser reduction in dryness/scaling/itchiness which was accompanied by significant but lesser decreases and increases in TEWL and capacitance values, respectively, at 2 and 4 weeks. Comparison of TEWL and capacitance values during the 4 weeks of treatment with CER or HIRU creams revealed that while the two parameters of CER cream-treated skin were generally similar to healthy control skin, those of the HIRU cream-treated skin remained similar to mild or moderate AD skin. Conclusion: It is likely that the recovery of barrier function reflects the improvement in clinically evaluated dry skin conditions of the nonlesional skin to a greater extent than that in water deficiency, which suggests that the barrier-replenishing effect is a more important factor for treatment of AD nonlesional skin than is the improvement of water deficiency.
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.
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