Our hair grows periodically, and the “lifetime” of each hair can be divided into 3 periods: 1. “2. The degenerative phase: After the growth phase, the hair enters the degenerative phase, the hair follicles start to shrink and the hair stops growing, this phase lasts about 2 to 3 weeks; 3. The “resting phase”: after the regressive phase, the new hair follicle cycle has not yet begun, the middle of this period of “silence” is the resting phase, the hair generally in this phase of their own shedding. The resting phase lasts about 3 to 4 months, after which the new hair will “sprout” on the same follicle and repeat the next growth cycle. When you are about 20 years old, there are about 100,000 hairs on your scalp, of which about 90% are in the growth phase, about l% are in the regression phase and about 8% are in the resting phase. A normal person will lose about 50 to 100 hairs a day, but don’t worry, there will be about the same amount of new hairs “sprouting” every day. If you lose more than 100 hairs per day on average and for more than 3 months, you should be alert and go to the hospital to find out the cause. Do not believe in the exaggerated advertisements of some businesses, but seek scientific treatment. Common factors leading to hair loss 1, nutrition (nutrient deficiency) 2, endocrine (postpartum, hypopituitarism, hyperthyroidism, etc.); 3, certain drugs (immunosuppressants, anti-tumor drugs, etc.); 4, diseases (long-term fever, tuberculosis, lupus erythematosus, etc.); 5, psycho-neurological factors (mental tension, excessive stress, etc.); 6, physical and chemical factors (hair dyeing, too tightly bound hair, etc.); 7, genetic Factors. The hair pulling test is a simple and easy way to check and signal hair loss, using the thumb, index finger and middle finger, gently pinch about 40-60 hairs from the root of the hair and stroke in the direction of the hair, if only 1 to 2 hairs fall out, it means it is generally normal; if more than 5 hairs fall out each time, abnormal hair loss is suspected. It is important to note that you should not wash your hair for at least 24 hours prior to performing this test.