Infant colds and fevers are categorized as respiratory infections, typically caused by pathogens such as respiratory viruses, bacteria, mycoplasma, and chlamydia. The initial symptoms usually manifest as varying degrees of fever. Subsequent general symptoms include appearing slightly less lively than usual, possibly accompanied by a reduced appetite, nausea, and even abdominal discomfort. The third category of symptoms affects the upper respiratory tract, commonly presenting as nasal congestion, runny nose, sneezing, and in some cases, coughing and excessive phlegm.