Selenium levels and skin diseases: systematic review and meta-analysis

Background: Several studies have investigated the association between selenium levels and skin diseases, but reached inconsistent results. Objective: This systematic review and meta-analysis was conducted to evaluate the association between selenium levels and skin diseases. Methods: A systematic search was conducted in public databases to identify all relevant studies, and studyspecific standard mean differences (SMD) and 95% confidence intervals (CI) were pooled to compare the selenium levels between different groups. Results: Twenty-seven studies were identified with a total of 1315 patient and 7181 healthy controls. Compared with controls, no significant difference in selenium was found in patients with vitiligo (SMD = 0.53, 95% CI: -0.40 to 1.45), alopecia areata (SMD = 0.47, 95% CI: -2.72 and 3.65), or eczema (SMD = 0.12, 95% CI: -0.24 to 0.48). A lower selenium level was found in patients with psoriasis (SMD = -0.62, 95% CI: -1.15 to -0.10), acne vulgaris (SMD = -1.02, 95% CI: -1.45 to -0.60), chloric acne (SMD = -2.35, 95% CI: -3.15 to -1.55), and atopic dermatitis (SMD = -2.62, 95% CI: -3.00 to -2.24). As for disease severity, severe patients had a higher selenium level than mild patients in psoriasis (SMD = 0.72, 95% CI: 0.07-1.38), but no difference was found in vitiligo (SMD = -0.26, 95% CI: -2.38 to 1.85) and alopecia areata (SMD = 0.46, 95% CI: -0.34 to 1.26). Conclusion: Selenium levels were associated with several skin diseases and the disease severity, and high selenium levels tended to be a protective factor in certain skin diseases.