Severe hair loss can be caused by hormone levels, autoimmune problems, and other causes such as infection and mechanical stimulation. 1. Hormone level: when the body’s sex hormone level secretion is too low, it is easy to cause hair loss, and smoking, bad dietary habits, irregular life, folliculitis and other reasons. 2. Autoimmune: If the body’s immune mechanism is damaged, it can also cause hair loss, including vitiligo, Hashimoto’s thyroiditis, goiter and other diseases. 3. Infection: when the hair follicle is infected by fungi, bacteria and other pathogenic microorganisms, causing serious damage, it is easy to cause permanent hair loss. 4. Mechanical stimulation: Secondly, if you often comb your hair hard and tie very tight braids, it is easy to cause pulling hair loss. All in all, there are many reasons for serious hair loss, not necessarily a physical problem. It is recommended that patients go to the hospital in time to complete a series of relevant examinations and strengthen daily life management to identify the specific causes.