Improvement of Nonlesional Skin Tone and Skin Barrier in Severe Atopic Dermatitis after Dupilumab Treatment

Dupilumab, approved for the treatment of moderate-to-severe atopic dermatitis (AD), has been proven to improve skin barrier and postinflammatory hyperpigmentation on nonlesional areas. Previous studies, however, are only based on subjective visual assessments rather than objective biophysical measurements. We aimed to objectively measure transepidermal water loss (TEWL) and skin tone improvements after dupilumab treatment through bioengineering devices. Nineteen patients with severe AD were enrolled. Biophysical measurements were conducted in three nonlesional skin areas, the cheek, forearm, and lower abdomen, on a monthly basis for 5 months since the first dupilumab injection. TEWL was measured using a Tewameter®. Skin tones represented by ${\mathrm{L}}^{\ast }$ (lightness), ${\mathrm{a}}^{\ast }$ (redness), and ${\mathrm{b}}^{\ast }$ (yellowness) parameters were measured by the spectrophotometer®; the erythema and melanin index measured by the narrow-band reflectance spectrophotometer® were additionally assessed. Improvement from baseline was evaluated by the Wilcoxon’s rank-sum test and Bonferroni correction. Correlation among biophysical parameters was evaluated by Pearson’s correlation. $p$ < 0.05 was considered statistically significant. TEWL and skin tone parameters in all anatomical regions showed significant improvement. The ${\mathrm{L}}^{\ast }$ and ${\mathrm{a}}^{\ast }$ values of the arm and trunk significantly improved after 2 months of dupilumab therapy and the face 3 months after. Similarly, ${\mathrm{b}}^{\ast }$ value of all anatomical regions significantly decreased after 1 month of treatment, and the TEWL did so after 2 months. When compared between anatomic regions, the trunk demonstrated higher improvement in ${\mathrm{L}}^{\ast }$ value, the arm in erythema index, and the face in melanin index. TEWL positively correlated with erythema index (r = 0.51, $p$ < 0.05), melanin index (r = 0.45, $p$ < 0.05), and ${\mathrm{a}}^{\ast }$ (r = 0.50, $p$ < 0.05); negative correlation was observed with ${\mathrm{L}}^{\ast }$ (r = −0.48, $p$ < 0.05). On top of AD symptom relief, dupilumab objectively improves the skin barrier and skin tone of nonlesional areas.