Colds can be caused by poor immunity or allergic rhinitis. 1. Poor immunity: It is easier to catch a cold than others and takes longer to heal. This kind of situation is mainly due to their own body immunity is poor, more sensitive to the external environment, belong to the susceptible people. Susceptible people need to exercise actively in order to improve their immunity; increase or decrease clothing in time to cope with changes in the external environment or temperature; take medication in time after catching a cold, and intervene early to speed up the process of recovering from a cold. 2. Allergic rhinitis: In clinical practice, there are many diseases with symptoms similar to those of colds, so they are mistaken for colds. For example, allergic rhinitis, allergic rhinitis often shows sneezing, runny nose, taking anti-cold medication has no obvious effect. In this case, oral montelukast or cetirizine can be taken, which is usually effective. Cold and flu is one of the most common diseases, people will also take their own oral medication, but if often recurring and the disease is too long to get better need to timely specialist consultation, do not blind treatment, so as not to aggravate the condition.