Abstract BACKGROUND: Despite the several studies suggesting the genetic basis of acne vulgaris, the exact genetic architecture of this very common condition is not yet clear. AIM OF THE WORK: This study aimed to investigate the association between IL-1A (-889) gene polymorphism and acne vulgaris in a sample of patients. SUBJECTS AND METHOD: Blood samples from 100 patients with acne vulgaris and 100 healthy age, sex, and BMI matched controls were obtained. DNA samples were isolated from blood cells, and the PCR-RFLP method was used for genotyping. RESULTS: The genotype distributions of IL-1A (-889) polymorphism were as expected under Hardy-Weinberg equilibrium. T allele was predominant in the patients, while C allele predominated in the control subjects (P value < .001). The frequency of TT genotype in patients was significantly higher than in the control subjects (P value < .001). CT genotype was significantly more frequent in the control subjects compared to patients (P value < .001). Among the 47 patients who reported diet as a risk factor for triggering or exacerbating their lesions, 62.5% had TT genotype (P value = .038). CONCLUSION: IL-1A (-889) gene polymorphism has a role in the pathogenesis of acne vulgaris. We suggest that the triggering or exacerbating effect of diet on acne may be related to IL-1A (-889) gene polymorphism. © 2018 Wiley Periodicals, Inc.