 This study examines the quality of systematic reviews, SRs, on the timing of complementary foods, CFS, for allergy prevention in infants and children. It finds that most SRs have low to critical low quality, due to poor reporting and lack of transparency. Additionally, only two SRs fully adhere to the preferred reporting items for systematic reviews and meta-analysis, Prisma, Checklist. Furthermore, several SRs fail to consider unpublished studies either by an explicit or priory exclusion or by inadequate search strategies. This suggests that the quality of SRs on the timing of CFS for allergy prevention needs improvement. This article was authored by Uwe Matan, Melissa Athe-Urik, Simone Probstel, and others.