Colds can be caused by poor immunity, wrong medication or overwork. 1. Poor immunity: When the patient’s immunity is poor, the stimulation of external microorganisms is likely to lead to the aggravation of the cold condition or the recurrence of the bad situation. 2. Wrong medication: When a person with a cold takes medication on his own, the medication may not be appropriate. This will not relieve the symptoms or control the cause of the disease, and may also lead to the recurrence of cold and flu. 3. Excessive exertion: When a person with a cold is overworked during the period of illness, it can also lead to a recurring condition that can’t return to normal. Colds can also be caused by other reasons, such as being cold. If other illnesses show symptoms similar to those of a cold, you should go to the hospital in a timely manner to get a clear picture of the cause under the guidance of your doctor and get the right treatment.