We evaluated the association between allergic conditions and the risk of glioma in case–control and cohort studies published so far on this issue. A total of 12 studies (10 case–control and 2 cohort studies) were included in the analysis, involving 61 090 participants, of whom 6408 had glioma. When compared with non-allergic conditions, the pooled odds ratio (OR) with any allergic conditions for glioma was 0.60 (95% CI: 0.52–0.69, P < 0.001), suggesting a significant negative association (protective effect) between allergy and glioma. Subgroup analysis showed that the ORs were 0.70 (95% CI: 0.62–0.79, P < 0.001), 0.69 (95% CI: 0.62–0.78, P < 0.001), and 0.78 (95% CI: 0.70–0.87, P < 0.001) for asthma, eczema, and hay fever, respectively. The significant association remained even after excluding the bias of proxy reporting (OR = 0.61; 95% CI: 0.50–0.75, P < 0.001). We conclude that allergic conditions may significantly reduce the risk of glioma.