When a child catches a cold, it is pneumonia, and the possible clinical causes are strong virulence of pathogens, immune deficiency of the child, and untimely treatment of upper respiratory tract infections. 1. Strong pathogen virulence: If the pathogen causing the child’s cold or respiratory tract infection has strong virulence, it is easy to spread to the lower respiratory tract through the upper respiratory tract, thus causing pneumonia. 2. Children with immune deficiencies: children with immune function abnormalities, their immunity is relatively low and unable to resist the invasion of pathogens and aggravation of the disease. 3. Inadequate treatment of upper respiratory tract infections: when a child has a cold, the symptoms can be controlled through continuous and effective medication, but if the parents do not carry out the relevant treatment in a timely manner, the child’s condition will be aggravated by the delay. Parents are advised to take their children to the hospital for an examination to determine the cause of the illness and to provide targeted treatment.