A cold, also known as an upper respiratory tract infection, is commonly caused by a decrease in immune function, leading to symptoms such as nasal congestion, runny nose, sneezing, sore throat, and fever due to viral invasion of the respiratory tract. Additionally, it is quite common for patients to experience varying degrees of cough during a cold. Due to the different pathogens that trigger colds, there is a significant variation in the clinical symptoms exhibited by patients. Naturally, the severity of symptoms also varies depending on the individual's immune strength. Thus, in treating colds, some patients might experience a dry cough initially and later develop a productive cough. These are both common occurrences, and effective control can be achieved with appropriate symptomatic treatment.