BACKGROUND: Melasma, a condition with complex and multifactorial pathogenesis, has traditionally been linked to factors such as ultraviolet (UV) exposure, hormonal changes, and genetic predisposition. Despite societal advances and shifts in lifestyle, updates on causal factors remain limited. Our study aims to address this gap by investigating emerging pathogenic factors that differ from those conventionally reported. OBJECTIVE: We conducted a case-control study to explore novel etiological factors contributing to the onset of melasma in Chinese patients, with an emphasis on how these differ from previously established causes. METHODS: The study included 150 patients (144 women and 6 men) diagnosed with melasma at Jiangsu Province Hospital of Chinese Medicine from April to October 2023. A control cohort of individuals without melasma was enrolled from the community. Demographic and clinical characteristics were collected, along with exogenous factors and histories of related dermatoses and non-dermatoses, through a questionnaire administered with the guidance of a dermatologist. Etiological factors were assessed using univariate analysis followed by multivariate analysis. RESULTS: Overall, our results were consistent with previous studies. In addition, alcohol intake (OR: 20.05, 95% CI: 1.17-343.17) and breast cystic hyperplasia (OR: 15.98, 95% CI: 4.28-59.72) were found to be novel triggering factors of melasma, whereas change of residence (OR: 0.03, 95% CI: 0.00-0.30), house renovation (OR: 0.13, 95% CI: 0.03-0.58) and soft drink intake (OR: 0.04, 95% CI: 0.00-0.83) were protective. CONCLUSION: These findings suggest that diet and the living environment are novel etiological factors for melasma.