Alopecia areata is a general term for hair growth disorders caused by various reasons. Since hair growth is influenced by various factors such as genetics, health conditions, hormone levels, medications and climate, when severe hair loss occurs symptomatic treatment needs to be given based on the identification of suspected triggers. Physiologically, the hair in the follicle follows a hair growth cycle from new growth to shedding, usually around 40 months. During this period, the hair is in the anagen phase for the first 36 months, followed by a regressive phase of 3-4 weeks and then shedding into a resting phase of 3 months, during which there is no hair in the follicle. The good thing is that the hair does not grow or fall out at the same time, about 80% of the hair is in the anagen phase, so as to maintain the normal total amount of hair, generally normal people physiologically shed less than 100 hairs per day, and there is an equal amount of new hair. In general, seasonal and climate change is most likely to cause short-term hair loss, usually within 2 to 3 months of natural relief recovery, no special treatment. If the hair loss lasts too long and the amount of hair loss is too much, first of all, you need to improve the blood routine, thyroid, liver and kidney function and other systemic examination to investigate metabolic, nutritional and other systemic diseases, some cytotoxic drugs in the treatment can also cause short-term massive hair loss, such as anti-tumor drugs. It can also recover naturally after removing relevant triggers in general. In addition, as we age, hair growth will also show a gradual decline, if the age of decline is too early, it is called “early baldness”, which is often referred to as “androgenetic alopecia”, “male pattern baldness “However, although the name of this type of hair loss seems to occur only in men, in fact, “early baldness” can occur in both men and women. This type of hair loss is obviously dominantly inherited, and individuals with a genetic background experience shrinkage of hair follicles in the hair loss area and shortening of the hair growth period under the action of hyperandrogenism, which leads to a decrease in the number of hairs in the anagen phase and an increase in the ratio of resting hairs.