- BACKGROUND: Upper respiratory tract infection in children is one of the most frequent reasons for visiting a family doctor, and antibiotics are often prescribed inappropriately. Sodium cromoglicate inhibits the ICAM-1 molecule, which is the receptor for human rhinoviruses. We aimed to investigate whether intranasal cromoglicate shortens duration of infection of the upper respiratory tract. METHODS: We randomly assigned 290 children diagnosed with suspected acute viral upper respiratory tract infection by their family doctor (137 boys, 153 girls; mean age 5.2 years [SD 3.39]) either intranasal 4% sodium cromoglicate spray or intranasal normal saline spray. Follow-up was by daily symptom diary for 2 weeks and by telephone. Canadian Acute Respiratory Illness and Flu Scale (CARIFS) score was the primary outcome measure. FINDINGS: 195 patients returned symptom diaries, and 20 of these could not be included in the main analysis. 246 patients completed the telephone interview at week 1. There was no difference in recovery rate over the first week between the two groups, with the estimated difference in slope of log (CARIFS) being -0.01 (95% CI -0.05 to 0.03). There were no differences between the two groups in side-effects or re-consultation rates. 43 (17%) of 246 children with suspected acute viral upper respiratory tract infection went back to see their family doctor, and 220 (89%) of 246 were managed without prescription of antibiotics. INTERPRETATION: Intranasal sodium cromoglicate is not a useful additional treatment for this infection. Our results further clarify the role of prescribed drugs for children with these frequent illnesses.