Especially easy to catch a cold, and the defense ability of the respiratory tract is reduced, it is difficult to resist the attack of various pathogens, common causes include immune factors, nutritional factors, environmental factors and disease factors. 1. Immune factors: patients who have bad habits, or suffer from systemic diseases, as well as mental and psychological long-term in a bad state, will cause a certain impact on their own immune system, so that pathogenic microorganisms are more likely to invade the body, causing the occurrence of colds. 2. Nutritional factors: If the body lacks certain trace elements, vitamins, etc., it will also lead to a decline in physical quality, which will easily lead to colds when in contact with pathogens. 3. Environmental factors: If you are in an environment containing harmful gases for a long time, your body will be stimulated by physical and chemical factors for a long time, and the defense ability of the respiratory tract will be greatly weakened, so when viruses and other pathogens invade the mucous membrane of the respiratory tract, you will have a cold. 4. Disease factors: If you have bronchiectasis, chronic obstructive pulmonary disease and other underlying lung diseases, the upper respiratory epithelial barrier function decreases, but also more likely to have a cold. In order to avoid frequent colds, we need to start from both external and internal factors: develop good living habits and open the windows indoors; for patients with underlying diseases, we should actively treat the primary disease; if the symptoms of colds are more serious, we must consult a doctor as soon as possible.