The shedding phase of alopecia areata generally lasts about three months. Alopecia areata refers to the sudden occurrence of patchy hair loss on the top of the head, usually caused by excessive mental stress, fatigue, and disorders of the immune system. Alopecia areata typically arises when various factors cause the hair follicles on the scalp to shift from the growth phase to the resting phase, resulting in the hair no longer growing and subsequently falling out extensively. The occurrence of alopecia areata is also somewhat related to genetics. If dieting leads to malnutrition, alopecia areata may also occur. The clinical manifestation of alopecia areata is the appearance of round or oval patches of hair loss on the top of the head. Some occur individually, while others may appear in multiples, varying in size and without any subjective symptoms. If alopecia areata occurs, it is advisable to seek diagnosis and treatment in the dermatology department of a standard hospital.