I read with great interest the article by Heydarian et al.The authors had conducted a clinical trial and found that zinc supplementation did not benefit clinical manifestations of acute bronchiolitis. The study is well described, but there are few points that need comment.The authors described that bottles of drug and placebo were similar in size and shape. However, it is well known that, the most important factor in zinc trials have been problem in blinding due to bad taste of zinc salts. There is also no description of the adverse events in the study (even in the zinc group), which is really surprising. So, author’s description of double-blinding might have been compromised, with resultant affection of the findings of the study. The authors also excluded children with pneumonia. But, how did they exclude children with viral pneumonia (as both are difficult to distinguish clinically and radiologically)? This is an important question, as it has been found that zinc might not be effective in viral pneumonia. It is also not clear, whether the person responsible for the administration of the intervention and evaluation of clinical signs of bronchiolitis is same or different. Because, if both have been done by the same person, then it might have also affected blinding and resultant data collection. These factors question the validity of the result.