Antibiotics are the most common type of medication prescribed to children, including infants, in the Western world. While use of antibiotics has transformed previously lethal infections into relatively minor diseases, antibiotic treatments can have adverse effects as well. It has been shown in children, adults and animal models that antibiotics dramatically alter the gut microbial composition. Since the gut microbiota plays crucial roles in immunity, metabolism and endocrinology, the effects of antibiotics on the microbiota may lead to further health complications. In this review, we present an overview of the effects of antibiotics on the microbiome in children, and correlate them to long-lasting complications of obesity, behavior, allergies, autoimmunity and other diseases.