Background: Pruritus has been reported as an adverse drug reaction to arsenic trioxide, but the association of arsenic exposure with pruritus has not been systematically investigated. To investigate the association of arsenic exposure with pruritus, we performed observational, interventional, and Mendelian randomization studies. Methods: A cross-sectional study was conducted in Shimen, China. A Mendelian randomization study was conducted to confirm the causal relationship between susceptibility to arsenic toxicity, in terms of genetically predicted percentages of monomethylated arsenic (MMA%) and dimethylated arsenic (DMA%) in urine, and chronic pruritus in the UK Biobank participants. Then, a case-control study in Shimen participants was conducted to determine the biomarker for pruritus, and arsenite-treated mice were used to confirm the biomarker. Last, a randomized, double-blind, placebo-controlled trial was conducted to test the efficacy of naloxone, a μ-opioid receptor antagonist, in arsenic-exposed patients with pruritus in Shimen. Results: Hair arsenic showed a dose-response relationship with the intensity of itch in 1092 participants. The Mendelian randomization analysis confirmed the causal relationship in the UK Biobank participants, with odds ratios of 1.043 for MMA% and 0.904 for DMA% above versus under median. Serum β-endorphin was identified as a significant biomarker associated with the intensity of itch. Consistently, treatment with arsenite in mice upregulated the level of β-endorphin. The randomized controlled trial showed that treatment with sublingual naloxone significantly relieved the intensity of itch in arsenic-exposed participants. Conclusion: Arsenic exposure is associated with pruritus, and β-endorphin serves as a biomarker of pruritus. Naloxone relieves pruritus in patients with [arseniasis](javascript:;).

Background Pruritus is identified as an adverse drug reaction to arsenic trioxide, but the association of arsenic exposure with pruritus has not been investigated. Methods A cross‐sectional study was conducted in Shimen, China. A Mendelian randomization analysis was conducted to confirm the causal relationship between genetically predicted percentages of monomethylated arsenic (MMA%) and dimethylated arsenic (DMA%) in urine with chronic pruritus in UK Biobank. A case–control study was then conducted to determine the biomarker for pruritus. Arsenite‐treated mice were used to confirm the biomarker, and von Frey test was used to induce scratching bouts. Last, a randomized, double‐blind, placebo‐controlled trial was conducted to test the efficacy of naloxone in arsenic‐exposed patients with pruritus in Shimen. Results Hair arsenic (μg/g) showed a dose–response relationship with the intensity of itch in 1079 participants, with odds ratios (OR) of 1.11 for moderate‐to‐severe itch (p = 0.012). The Mendelian randomization analysis confirmed the causal relationship, with ORs of 1.043 for MMA% (p = 0.029) and 0.904 for DMA% (p = 0.077) above versus under median. Serum β‐endorphin was identified as a significant biomarker for the intensity of itch (p < 0.001). Consistently, treatment with arsenite upregulated the level of β‐endorphin (p = 0.002) and induced scratching bouts (p < 0.001) in mice. The randomized controlled trial in 126 participants showed that treatment with sublingual naloxone significantly relieved the intensity of itch in arsenic‐exposed participants in 2 weeks (β = −0.98, p = 0.04). Conclusion Arsenic exposure is associated with pruritus, and β‐endorphin serves as a biomarker of pruritus. Naloxone relieves pruritus in patients with arseniasis.

To investigate the clinical characteristics of skin disorders among hospitalized patients before and during the coronavirus disease 2019 (COVID-19) pandemic, a retrospective study was conducted based on hospitalized patients with skin diseases from Xiangya Hospital of Central South University, the largest hospital in the southcentral region of China, between January 1, 2018, and December 31, 2021. A total of 3039 hospitalized patients were enrolled in the study, including 1681 patients in the prepandemic group and 1358 patients in the pandemic group. The total number of hospitalized patients in the pandemic group decreased by 19.2%, with an increased proportion of patients over 60 years of age (39.8% vs. 35.8%). Moreover, compared with the prepandemic group, there were decreases in the occurrence of most skin diseases in the pandemic group, but the proportions of keratinolytic carcinoma (6.6% vs. 5.2%), dermatitis (24.0% vs. 18.9%), and psoriasis (18.0% vs. 14.8%) were higher in the pandemic group. In addition, longer hospital stays (β = 0.07, SE = 0.02, P = 1.35 × 10 −3 ) and higher hospital costs (β = 0.06, SE = 0.03, p = 0.031) were found in the pandemic group through general linear models, even after the corresponding adjustment. In summary, the COVID-19 pandemic has had a lasting impact on patients with skin diseases, with fewer hospitalized patients, increased proportions of older patients, longer hospital stays, and increased hospital costs. These findings will facilitate better preparation for the most effective response to future pandemics.