Colds are infections of the upper respiratory tract and are generally not very likely to cause bronchitis and pneumonia if treated aggressively. Bronchitis and pneumonia are infections of the lower respiratory tract, so when you have a cold, you should take rest, drink more hot water, and use antipyretic drugs or targeted anti-pathogenic drugs for the cause, such as viruses or bacteria, to prevent the cold from entering the lower respiratory tract and causing bronchitis and pneumonia to a large extent. The elderly, children and people who have insufficient immunity due to special medication, or people who do not rest well or stay up late often, may not be able to interrupt the course of the cold in time, leading to further invasion of internal organs, which can lead to bronchitis and pneumonia. Therefore, rest and nutrition are especially important when treating a cold, and one should also take plenty of water in time.