This is a multi-center, randomized, double-blind, placebo-controlled study designed to better understand whether the choice of antibiotic affects symptom burden in children with acute sinusitis (AS). Children enrolled in the study are randomly assigned to receive amoxicillin, amoxicillin-clavulanate, or a matching placebo. Neither the families nor the study team know which treatment a child is receiving during the study period. The primary objective is to compare average daily symptom severity across treatment groups using validated caregiver-reported symptom scales collected through daily electronic diaries. Analyses will assess whether symptoms suggestive of allergy (sneezing or itchy eyes) or more severe nasal findings (such as marked congestion or perinasal crusting) influence treatment response. The goal is to provide rigorous, comparative evidence on antibiotic use in this common pediatric infection to support more informed clinical decision-making and responsible antimicrobial prescribing. The study will also examine whether factors such as the severity of the child's illness and signs of allergies affect how well antibiotics work. The results will help guide better treatment decisions for children with sinus infections
