Hair loss with more hair on one side and less on the other side may be related to physical hair loss, pathological hair loss and androgenetic alopecia. 1. Physical alopecia: If the patient’s unilateral hair is often tied high, it will lead to unilateral hair being pulled by gravity, causing hair loss. It is also possible that the patient often sleeps on one side of the bed, and the repeated friction causes the hair on one side to become less. 2. Pathological alopecia: If the patient has patchy baldness on one side of the head, it may lead to unilateral lumpy hair loss, resulting in less hair on one side. If there are diseases such as folliculitis, boils and fungal infections on one side of the head, the normal hair follicles may be affected, leading to destruction of the hair follicles and localized alopecia, resulting in less hair. Patients with androgenetic alopecia may have thinner hair on the top of the head, or may have slightly less hair on one side. Considering the complexity of the causes, patients are advised to actively seek medical treatment, do systematic examination, and treat the symptoms after clarifying the causes.