Alopecia areata starts as one or several well-defined circular or oval hair loss areas, with straight plays about 1 to 2 cm larger. The edge of the hair loss area often has some loose and easy to lose hair, some have been broken, near the lateral end of the hair often atrophy. If the hair is pulled out, the hair can be seen on the thick and thin like an exclamation mark (!) The lower part of the hair is also depigmented. As the hair loss continues to increase, each piece expands and can fuse with each other to form an irregular shape. If it continues to progress, it can be completely bald. In severe cases, eyebrows, eyelashes, axillary hairs, pubic hairs and all over the body hair are also lost to form a general baldness. There are two main types of alopecia areata: one is seborrheic alopecia, which accounts for about 70% of all patients with alopecia areata. One is neurogenic alopecia, which accounts for about 29% of all alopecia patients, and only about 1% of alopecia caused by other reasons, such as ringworm and syphilis. With the development of society and the accelerated pace of people’s life, work and study, the psychological pressure on people is increasing, and the incidence of hair loss in the population is getting higher and higher. What are the diagnostic criteria for alopecia universalis? 1.It can occur at any age, but is more common in young adults. 2. It often occurs after excessive exertion, lack of sleep or mental stimulation. 3.Usually there are no conscious symptoms, or itching, but it may also be accompanied by dizziness, dizziness, distraction, insomnia, and dreaminess. 4.The onset of the disease is sudden, and patients mostly find that their hair starts to fall out unintentionally until it is called total baldness. Then the eyebrows, beard, internal hair and pubic hair are also completely lost, and the fine hair may also be lost, completing the general baldness. 5. The course of the disease is slow and the length of time varies. However, the disease may last for several months or longer because it is easy to shed again. At the time of recovery, new hair grows out from the affected area, initially thin and soft, yellowish or grayish, gradually becoming thicker, harder, darker, and finally the same as healthy hair.