Reevaluation of the Importance of Barrier Dysfunction in the Nonlesional Dry Skin of Atopic Dermatitis Patients through the Use of Two Barrier Creams

<i>Background:</i> 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. <i>Objective:</i> 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. <i>Methods:</i> 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. <i>Results:</i> 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. <i>Conclusion:</i> 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.