BACKGROUND: Magnesium is essential for epidermal differentiation and immune regulation and dysregulated magnesium homeostasis has been implicated in chronic inflammation. However, its association with inflammatory skin diseases has been poorly characterized. OBJECTIVE: To investigate whether abnormal serum magnesium levels are associated with increased risk of psoriasis, atopic dermatitis, and acne in a real world population. METHODS: Using the TriNetX multicenter database, adults aged 18-65 years with hypomagnesemia (serum magnesium 0.0-1.6 mg/dL) or hypermagnesemia (2.6 mg/dL) were identified on November 12, 2025 (query range 2008-2025) and propensity score matched 1:1 to controls with normal magnesium levels. Matching variables included age, sex, race, ethnicity, chronic kidney disease (stages 1-5), bariatric surgery, and alcohol related disorders. Risk ratios (RR) and odds ratios with 95% confidence intervals (CIs) were calculated using logistic regression. Significance was set at p<0.05. RESULTS: After matching, 246,648 patients with hypomagnesemia and 86,649 patients with hypermagnesemia, as well as respective controls were included. Hypomagnesemia was associated with significantly increased risk of psoriasis (RR 1.173; 95% CI 1.098-1.253; p<0.0001) and atopic dermatitis (RR 1.091; 95% CI 1.027-1.160; p=0.0051), but not acne (RR 0.971; 95% CI 0.931-1.014; p=0.1843). Hypermagnesemia was not significantly associated with psoriasis, atopic dermatitis, or acne (all p 0.05). CONCLUSION: Hypomagnesemia, but not hypermagnesemia, was associated with increased risk of psoriasis and atopic dermatitis. These findings suggest a potential role for magnesium deficiency in cutaneous inflammatory pathogenesis and warrant further mechanistic and longitudinal studies.