Impact of oral bacterial lysates on asthma control and immune parameters in children: evidence from an updated systematic review and meta-analysis of randomized trials

Background The role of oral bacterial lysates (OBLs) as adjuvant immunomodulatory therapy in pediatric asthma requires clarification. This systematic review and meta-analysis evaluates their efficacy and safety. Methods We searched eight databases for randomized controlled trials (RCTs) in children comparing standard asthma therapy plus OBLs versus standard therapy/placebo. Primary outcomes were clinical (wheezing/infection frequency, symptom improvement time, treatment efficacy) and lung function parameters. Secondary outcomes included immune biomarkers and adverse events. Random-effects meta-analyses were performed. Results Twenty-eight RCTs (n = 2,893) were included. Adjunctive OBLs therapy significantly reduced wheezing/exacerbation frequency (Mean Difference (MD) = −3.00,95% confidence intervals (CI): 4.07 to −1.93), shortened symptom improvement time (MD = −3.13 days, 95%CI: 4.10 to −2.15), reduced Respiratory Tract Infection (RTI) frequency (MD = −2.43,95%CI: 3.62 to −1.23) and increased overall treatment efficacy rate (relative rates (RR) = 1.17, 95%CI: 1.13–1.21). Improvements occurred in lung function (Forced Expiratory Volume in 1 s [FEV1], Forced Vital Capacity [FVC], Peak Expiratory Flow [PEF]) and immune parameters (increased the level of T-lymphocyte subsets (CD3+,CD4+,CD4+/CD8+) and salivary secretory immunoglobulin A (sIgA), decreased peripheral eosinophil (EOS) count and the level of interleukin-4(IL-4), eosinophil cationic protein (ECP), fractional exhaled nitric oxide (FeNO). Adverse events did not increase significantly (RR = 1.26, 95%CI: 0.93–1.70). Subgroup analyses showed consistent benefits across follow-up duration, age, and sample size, with background inhaled corticosteroids (ICS) therapy being a potential effect modifier (P = 0.06). Conclusion Adjunctive OBLs therapy is associated with improved clinical outcomes, lung function, and immune modulation in pediatric asthma, with a favorable safety profile. However, methodological limitations, substantial heterogeneity, and potential biases warrant caution. While promising, more rigorous and long-term trials are needed to define its precise therapeutic role and target population. Systematic Review Registration Identifier CRD420261281796.