This research aimed to evaluate the impact of probiotic supplementation on the severity of psoriasis symptoms and its association with the risk of developing the disease. We analyzed the association between probiotic usage and psoriasis among 21,942 participants from the 2009-2014 NHANES, employing advanced machine learning techniques for data analysis. A separate meta-analysis was conducted to assess the effects of probiotics on the severity, life quality, and some related inflammation factors. Dichotomous data were analyzed using odds ratios (ORs) corresponding to the 95% confidence interval (CI). Analysis of NHANES data did not reveal a statistically significant association between probiotic intake and the risk of psoriasis. However, the meta-analysis indicated that probiotic supplementation significantly lowers Psoriasis Area and Severity Index (PASI) scores both for change in PASI score and post-data change, and enhances PASI 75 (OR = 4.80, 95% CI = 2.92-7.89) and clearance responses (OR = 3.14, 95% CI = 1.99-4.96), as well as reduced levels of inflammatory markers. While the improvement of life quality was only observed in the post-treatment data. While probiotic supplements do not appear to reduce the risk of psoriasis, they have a significant positive effect on reducing disease severity. Registered on PROSPERO: Registration number CRD42023484417.